Industrial and Engineering Chemistry : industrial edition, Vol. 19, No. 7

Cellulose and Conservatism

r pH R O U G II the achievem ents of chem istry the products of cellulose have figured largely in the new com petition between industries for the privilege of serving a consuming public. Cellulose has been designated as the field in which the next great chemical discoveries w ill be made, just as coal tar has provided the raw material par excellence of the present generation. A fter all, we know very little about cellulose, and thus far in none of the great universities or other research centers of the U nited S tates have there been provided adequate equipm ent and generous endow m ent for the prosecution of th a t basic research w ithout which proc­

esses in many industries depending upon cellulose m ust con­

tinue upon their em pirical w ay.

We may soon find com petition betw een various sources of cellulose for th e business of supplying the great tonnage of raw material which the future seem s certain to demand.

Wood, possessing the advantage of being a material for the handling of which w e are fairly well organized, easy of stor­

age, furnishing concentrated cellulose for transportation, and having none of the disadvantages of a cereal crop, is still looked upon w ith favor, notw ithstanding its high cost, the scarcity of som e varieties, and th e problems of refores­

tation that are involved in its continual use on an enormous scale. We still consider cellulose too much from the stand­

point of fibers and the length of fibers required for satis­

factory paper manufacture. As a result, thousands of tons of our finest pulp, still necessary for the best grades of paper, have found their w ay into chemical processes in w hich it would seem that the length of fiber can have no importance.

The efficient use of such resources clearly indicates the de­

sirability of learning how to use th e other woods th at are available] some of them of com paratively rapid growth, for the production of the cellulose w hich the chemical industry demands. Cellulose satisfactory for chemical work is al­

ready produced from other sources a t a price to compete with wood pulp, and other new raw m aterials remain to be utilized.

The story of cotton linters and of short-fibercd cotton is well known, and cellulose from cotton is preferred for some varieties of rayon, for nitrating, and a number of special uses. The advantages w hich m ight accrue to the South through new m ethods for handling cotton m ay place this source of cellulose in a still more favorable position. A sub­

stantial quantity of cotton has already been grown in Texas by a method which involves a certain am ount of broadcasting seed in place of drilling it in rows, blocking, and thinning to allow the cotton plant to branch as a tree and bear m any bolls at different heights. T he new m ethod produces in­

stead a stand of plants w hich mature their cotton on approx­

imately the same level. T his permits m achine picking and reduces the cost of production to a degree w hich seem s alm ost revolutionary. T he resulting fiber m ay be sligh tly inferior from the textile, but n ot from th e chemical, point of view , and mdeed may play an im portant part in providing an economic

outlet for cotton through rayon, the fiber th at offers cotton textiles such active competition.

Announcem ents, made principally through the lay press, promise cellulose from another source th at is plentiful though w idely scattered and adm ittedly offering problems in col­

lection, handling, transportation, and storage w hich are more difficult than the technicalities involved in processing this cellulose. E very generation or so an attem pt has been made to utilize a portion of the v a st am ount of farm w astes repre­

sented by cereal straws and cornstalks. Previous efforts differ from the present one in tw o major respects. Here­

tofore, whether or not the cellulose could be used depended upon its adaptability to the paper industry. Secondly, the treatm ents em ployed closely resembled those practiced in wood technology. T he present investigators believe that this w as unnecessarily drastic. T h ey refer to the differ­

ences between the lignins present in wood and the substan­

tially softer and weaker mucilaginous substances adequate for holding together the fibers in an annual plant. There­

fore, instead of using high concentrations of caustic, which demand the recovery of sodium hydroxide to m ake th e proc­

ess economical, th ey propose to use a concentration so low th at in preparing estim ates they have disregarded the possi­

bility of caustic recovery. High pressures ty p ify the di­

gestion of w ood and, arguing on the basis as above, those w ho w ould utilize cornstalks propose to carry o u t their treat­

m ent in tw o stages— the first a t atm ospheric pressures and the second a t not more than tw o atm ospheres— both of com ­ paratively short duration. T his treatm ent, according to the tests on a laboratory scale made in this country, indicates the possibility of utilizing the entire cornstalk, including tassel and leaves, w ith a yield on a bone-dry basis of approx­

im ately .30 per cent of bleached cellulose. If this can be done on a commercial scale and if the cellulose when produced in q uantity proves satisfactory to the rayon manufacturer, the nitrator of cellulose, and other chemical industries de­

siring this raw material, then it m ay be possible to make from approxim ately 3 tons of stalks a q uantity of cellulose comparable to th a t derived from 2 tons of wood.

W e com e a t once to the sam e old story of the econom ics involved in the industry. W ith th e optim um sized plant reckoned a t 50 tons per day, 150 tons of cornstalks would be required, and in the corn b elt proper it has been estim ated th at such a qu an tity can be obtained w ithin a radius of truck hauling n ot beyond the possibilities in these days of modern highw ays. I t is proposed to resort to baling in order to truck a load of profitable size and to minimize the expense and possible fire hazards involved in handling an annual crop.

T o make it attractive from the farmer’s view point, it has been suggested th a t th e com pany supply th e m achinery and labor for cutting and baling the stalks and pay the farmer a few dollars per acre for the privilege. T he engineering departm ents of agricultural experim ent stations and the developm ent departm ents of th e agricultural machinery m anufacturers have for som e tim e been w orking on types of mobile m achines th a t are to cut, husk, and then bale the

t

766 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 19, No. 7

stalks, thereby sim plifying the problem of corn-harvesting and reducing the present cost of 7 cents a bushel for corn- husking. T he threatened necessity for com pletely removing stalks from th e surface of a field in an effort to defeat the corn borer is a new factor favoring collection.

M an y view s are held as to the possibility of doing all these things on a commercial basis. T he question is not so much w hether the products claimed can be produced from corn, or from any other source of cellulose. T he real point is w hether or n ot m oney can be made by such operations. Pros and cons m ay be presented by enthusiasts, but th e only real answer is a practical dem onstration. W e are promised such a dem onstration through the m edium of a 10-ton pilot plant, the site for which has been selected, and w e understand that plans for its erection are progressing. Ten tons of cellulose per day w ill give a q uantity w ith w hich factory-scale ex­

perim ents can be m ade to determ ine the uses for which it is suited. There w ill be an opportunity to prove the effi­

ciency of the harvesting machinery and to try out on the high­

w ays th e economical hauling of baled stalks. Fortunately, all this is to be done -«nth the m oney of a group supporting the project w ith their eyes w ide open. N o effort is to be made to interest the public generally until sufficient data have been obtained on large-scale operations to back up state­

m ents as to possible profits and to answer the questions in th e minds of all doubters. I t is profoundly to be hoped that in the interim the interest aroused through the publicity given these proposals will not be exploited b y blue-sky salesmen.

W e think one further point should be kept in mind— that w hile it m ay prove possible to manufacture m any tons of cellu­

lose from cornstalks, and w hile thousands of other tons m ay find their w ay into w all boards and boards to com pete w ith straw board, such developm ents, however im portant, cannot be looked upon as a solution of the much discussed farm prob­

lem. Such industries w ould unquestionably help a number of farmers, but it seem s idle to speak of their im portance in terms of all the cornstalks that are grown or any considerable portion of them . T h e market surely is n ot ready to absorb wall board at a rate of 5 or 6 tons per capita annually in the U nited States, nor are th e numerous ou tlets for cellulose m a­

terials great enough to consum e all the cellulose th at m ight be made from such a tonnage.

Scientists have long since ceased to be prophets, for they know that the im possible is achieved alm ost daily. So far as cellulose is concerned we shall make no prophecy, but in­

stead urge conservatism and an inquiring state of mind until circum stances perm it a detailed technical discussion of w hat is involved and doubts are answered b y dem onstration.

More Methanol

T N T H E m anufacture of butanol b y th e ferm entation of corn a large volum e of gas is generated— a mixture of hydrogen and carbon dioxide. I t has long been known in technical circles th a t the Commercial Solvents Corporation proposed to m ake th e m ost of th is w aste hydrogen in the fixation of atm ospheric nitrogen, and a plant which proved capable of producing 100 per cent above its rated capacity w as erected and operated for this purpose. H ow ever, this involved w asting a considerable volum e of carbon dioxide and research w as undertaken to use both hydrogen and carbon dioxide for the m anufacture of m ethanol.

So far as w e know, the first commercial plant to prepare pure syn th etic m ethanol by catalytic reaction betw een hy­

drogen and carbon dioxide is now in operation under this com pany’s m anagem ent and th e volum e of American-made synthetic m ethanol has been trebled by this procedure. This is a neat piece of work, w hich enables the com pany to m anu­

facture either amm onia or m ethanol as m arkets and other conditions m ay require. I t is to be congratulated upon the successful outcom e of research w hich has led to a group of' patents for the protection of this novel process.

A reduction in w aste has been accom plished and a new source of supply for an im portant solvent found. Doubt­

less w e can look for further progress as a result of additional ' work still in the stage of incom plete research.

An Important A ccession

n P H E statem ent, of Judge Gary th a t the United States Steel Corporation has decided to undertake an impor­

ta n t program of research brings a m ost encouraging accession to the ranks of those industries w hich have science upon their payrolls. For years the steel industry has been pointed out as one depending for its financial success more upon tonnage and marvelous mechanical devices than upon fundamental research. T he apparent lack of interest in scientific work of the U nited States Steel Corporation in particular has, in fact, hindered the com plete alliance betw een industry and science w hich m any regard as so im portant to American in­

dustry. T his restraining influence is now to disappear.

T his great corporation is to set up w hat appears to be an ideal organization for its purposes.

T he finance com m ittee is to be the supreme authority and under its auspices there has been established a Depart­

m ent of Research and Technology. T he director of this de­

partm ent is John Johnston, for som e tim e past the chairman of the D epartm ent of C hem istry a t Y ale and a man promi­

nent in the activities of the Am e r i c a n Ch e m i c a l. So c ie t y.

D r. Johnston is to have the advice and assistance of an exec­

u tive council made up in part of leading scientists in this country and in part of men from the subsidiary companies of the Steel Corporation. T itles and organization may be shifted to m eet situations as th ey arise, but it is intended to utilize to the full the skill, experience, enthusiasm , and energy of the present em ployees of the various companies of the corporation in initiating and prom oting work to secure the best results.

In discussing industrial research we, in common with others, have frequently stressed the cardinal points of successful achievem ent. These include the choice of a competent direc­

tor of the work. H is training and experience, his achievements as a scientist, his adm inistrative ability, his tact, diplomacy, and courage lead us to venture the opinion th at in Dr. John­

ston the finance com m ittee has selected an ideal man for this post. A nother requisite is adequate financing. Judge Gary says that, w hile the corporation has “no money to w aste intentionally', w e have m oney to expend if necessary.

As for facilities, “w e intend to give him th e tools to enable him to work m ost successfully.” N o decisions have as yet- been made w ith respect to new laboratories. Recommen­

dations as to general policy will n ot be made until after the new director and the executive council have had an oppor­

tu n ity to visit the m ain plants and laboratories of the sub­

sidiary companies to receive and consider suggestions from the men fam iliar w ith the industry.

As for continuity of work, “w e aim to establish and mam- j

tain a D epartm ent of Research and T echnology.” Johu E. T eeple coined th e phrase “ patient m oney,” and we all

know the im portance of th a t attribute. M an y research

projects bravely begun have come to naught through the im patience of the m oney. I t is therefore gratifying to read in Judge G ary’s statem en t to th e research committee of th e corporation: “W e do not expect you can go along at a very rapid rate to begin w ith , or perhaps a t a n y tim e, but we will have the patience, as you m ust all have patience. R em em b er

July, 1927 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 767 so far as discovering anything new or making any new sug­

gestions is concerned, although th e work w ill be done in a methodical w ay, every one of you has a very 'b ig responsi­

bility and w e think it will n ot be so very long— and I do not measure tim e b y m onths or years— before you w ill have justified our decision in starting this departm ent.”

Another essential is the choice of a sufficient number of important problems, and w e all know th at in such a vast industry so m any problems m ust exist as to afford a long list from which to m ake careful selections.

We rejoice in the decision of the Steel Corporation, its director has our best wishes, and th e progress of the work will be followed w ith keen interest. W e predict a successful outcome.

Unnecessary Hazards

W

tion of a hazard enters, the burden of proof should rest w ith those offering the new m ethod and should not involve the expenditure of public funds.

Lead costs approxim ately one-tenth as much as tin, and this has been a factor in th e adoption of a m ethod for the weighting of silk in which tin-lead phosphate is the raw ma­

terial rather than tin tetrachloride. T he lead becomes fixed in the fiber as lead oxide, lead phosphate, or som e combi­

nation of the tw o. Besides being a much cheaper process, silk weighted w ith lead salts seem s to deteriorate more slowly than silk weighted w ith tin. There are some disadvantages.

For instance, som e of the lead is extracted in the benzene baths used by dry-cleaners and is ready to combine w ith the sulfur which m ay be brought into the baths in wool. T he dry-cleaners have already had som e difficulty, since they are not familiar w ith all the characteristics of the garments th ey treat; an occasional w hite flannel su it has been both cleaned and turned gray in one operation. Lead-weighted fabrics are also sensitive to the hydrogen sulfide in the air and the lighter shades turn dark on exposure and m ay eventually turn almost black. Fancy w hat com m ents m ay be m ade con­

cerning the dye and the dyer w hen this takes place, and think how many laundry owners and dry-cleaners, w ithout a chemist to make an adequate defense, w ill make settlem ent for damage laid to them rather than risk the anger of a dis­

satisfied customer! I t is doubtful w hether the real culprit will be apprehended and trouble is m ade all along the line because some one, for an initial price advantage, puts a proc­

ess into practice w ithout giving thought to all the ills that may be involved.

Although scientists generally agree that lead poisoning is clue more to inhalation or ingestion of lead dusts, cases of poisoning from the free application of lead plaster have been reported. M uch of the lead-weighted silk finds its w ay into commerce in underwear and it is a question whether lead m silk on coming into contact w ith the various secretions of the skin might not be absorbed to som e extent, for it is found that such silk treated w ith 3 per cent acetic acid a t body tem ­ perature does lose som e of th e w eighting material. I t m ust also be remembered th at lead is a cum ulative poison and, while the hazard m ay be slight, individuals who m ight ques­

tion the desirability of w earing a lead-weighted garment should he given the facts and allowed to make their own decision.

At first thought this w ould seem to be a problem for the Public Health authorities, bu t it is hardly fair to ask the pub­

lic to pay for an investigation th e outcom e of w hich concerns first and foremost those engaged in the business of w eighting

silks. T he public is n ot endangered by tin-w eighted silks, and it seem s clear to us th at if such investigations were to be m ade som e other than the public treasury should bear the expense. T he difficulty of the problem is apparent, for all silks are not w eighted to the sam e degree. T h ey are n ot subjected to the sam e number or kinds of laundering oper­

ations, are not worn for equal periods or under the sam e con­

ditions b y various individuals and, w hat is even more dis­

concerting, individual idiosyncrasies m ust be considered.

Speaking for ourselves, if wre m ust have w eighted silks, we prefer a tin shirt to a lead one, and w e think our fellow suf­

ferers should be given the information and the opportunity to choose for them selves. In particular, w e protest th e un­

necessary exposure of the public to a potential hazard, the ex­

istence of w hich is h o t dictated b y an y fundam ental consider­

ation.

Science in the Saddle

n p I I O S E representatives of the chemical industry who dur- ing the past several years have come in contact w ith J. M . D oran look upon his appointm ent as Prohibition Com­

missioner as a promising sign th at legitim ate industry will be guaranteed minim um annoyance in securing adequate supplies of the chemical raw material, alcohol. A t the same tim e those w ho are more concerned w ith law enforcem ent than w ith an y industrial consideration feel confident th at D r. D oran’s attitu d e regarding the E ighteenth Am endm ent, and his appreciation of the complex difficulties arising from th e enforcem ent of the laws relating thereto, give promise of an adm inistration as nearly satisfactory to them as popular opinion w ill a t present permit. For all concerned, therefore, we feel th a t the promotion of this chem ist to his present place of authority not only is deserved but is a w ise step on the part of the A dm inistration.

I t has been our privilege to work for days a t a tim e in groups representing extrem ists of both factions and to see examples of straight thinking and courageous decisions b y Dr. Doran in his capacity as chief chem ist of th e U nit.

W ith th e cooperation of his professional colleagues w hich the present Prohibition Commissioner has a right to expect, the law-abiding chemical industry m ay look forward to the developm ent of conditions which, in contrast w ith th e past, will help rather than interfere w ith its legitim ate operations.

D iscovery

C O M E students of invention believe th at world develop-

^ m ent leads to conditions which practically force into being discoveries th a t are needed for a continuation of prog­

ress. W hile m any inventions arc perfected in advance of their need, others seem to appear in plenty a t ju st the right tim e. M any examples m ay be cited, including the well- known fact th at the applications of Alexander Graham Bell arrived a t the P atent Office a scant five hours before those of another inventor covering practically the sam e ground. The records of the P aten t Office testify to the frequency w ith w hich applications are made to patent the sam e thing inde­

pendently discovered b y m any other inventors. These numerous examples raise th e question whether the inventor’s success does n ot involve a large elem ent of luck in being the first of m any applicants to obtain the basic patent in an age conducive to the developm ent of genius.

T his is brought to m ind b y the sim ilarity betw een the m ethod suggested b y Mr. Bond in our M ay issue and one published b y H . L. Payne, of our L os Angeles Section, in 1892. We print in this issue a note from Mr. Bond on the subject. T his is a clear case of independent discovery, w hich of course m ay occur in chem istry as w ell as in the other sciences and the arts.

768 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 19, No. 7

A Sulfate of A m m onia P lan t1

B y F . A . E r n s t a n d W . L . E d w a rd s

Fi x e d Ni t r o g e n Re s e a r c h La d o r a t o r y, Bu r e a u o r So i e s, Wa s h i n g t o n, D . C.

S

sideration as a consumer of any further increase in synthetic amm onia production in this country.

Ammonium phosphate has an advantage over the sul­

fate in th a t phosphoric acid, the amm onia carrier, is itself a plant food. I t has the disadvantage, however, of being dependent upon phosphoric acid, th e econom ical produc­

tion of w hich in a concentrated form is still under investi­

gation. A lthough th e production of concentrated acid through the reduction of phosphate rock in either electri­

cally heated or fuel-fired furnaces has been the subject of investigation for a number of years and has been worked out technically, this acid has not proved economical for fer­

tilizer use.

A sulfate of amm onia plant can be so constructed and erected as to be available w ithout alteration for the pro­

duction of am m onium phosphate from concentrated phos­

phoric acid and ammonia. I t is w ith this thought in mind that th e following brief description of the construction and operation of a sulfate of amm onia plant is given.

M e th o d s o f P r o d u c tio n

U tilizing sulfuric acid, am m onium sulfate m ay be pro­

duced by cither the cold or hot m ethod.

In th e first m ethod, usually em ployed a t the by-product coke ovens, the gas containing 1 to 2 per cent of amm onia as it comes from the ovens is partly cooled and passed through th e tar extractor to the am m onium sulfate saturator con­

taining dilute sulfuric acid. T he resulting salt is ejected from the saturator to the drain tables or settling boxes, w hile the gas m inus its amm onia passes out through an acid trap.

gas and the saturator m aintained a t 100° C. (212° F.). The excess water in this case passes off as steam .

F lo w D ia g r a m

The flow for this operation is shown in Figure 1. From an acid supply the 60° B 6. sulfuric acid flows by gravity through a measuring box to the tower distributor, over the checkered packing of the absorption tower, and into the saturator.

Am m onia gas brought in through a m ain enters the sat­

urator through the am m onia distributor, from which it bub­

bles up through the liquor w hich absorbs it. A ny ammonia not absorbed passes ou t into the tower, where it is picked up b y the descending acid spray and returned to the saturator.

B y m eans of the steam ejectors, the resulting crystal­

laden liquor is ejected to the trough serving the settling boxes. In these boxes the crystals are perm itted to build up while the liquor drains off to the return trough and is returned to the saturator. W hen sufficient crystals have collected in the settling box, th ey are raked to the centrif­

ugal drier, where th ey are wrung free of the larger part of th e liquor. Final drying takes place in the rotary drier, from which the sulfate m ay be removed to storage.

C o n d itio n s o f O p e r a tio n

B ecause the size of the crystals decreases as the acidity of the saturator is increased, it is very im portant to maintain this acidity a t a low concentration. In plants using by­

product coke-oven gas the acidity is m aintained at about 2.5 per cent. T his is possible because this gas, as previously m entioned, is relatively low in amm onia. I t would not be practicable when utilizing 100 per cent amm onia gas, how­

ever, to drop this acidity below 4 per cent, the range

T he saturator in this case is m aintained a t about 60° C.

(140° F .). T he excess w ater introduced w ith the sulfuric acid and as wash w ater is carried off w ith the large volum e of gas passing through the saturator.

In the hot m ethod, w hich w ill be discussed here, the am ­ m onia is introduced as practically 100 per cent amm onia

1 R e c e iv e d A pril 2 7 , 1927.

being usually 4 to 7 per cent sulfuric acid. The acidity of the saturator for purposes of this paper will be considered as being 7 per cent.

T he reaction w ith heats of form ation per mol from the elem ents, for the substance in th e sta te indicated, is:

2 N H 3 (gas) + H sSO, (7% ) = (N H ()2S 0 4 (aq.) 23,780 cal. 209,680 cal. 281,000 cal.

July, 1927 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 769 The heat evolved, therefore, is 47,540 calories per m ol of

sulfate. In addition there is evolved a heat of dilution of acid 77.67 per cen t (60° B 6.) sulfuric acid to 7 per cent of 8669 calories per mol. T he to ta l heat evolved, then, is 47,540 + 8669 = 56,209 calories per m ol of sulfate.

so as to build up a cake of uniform thickness. A t the sam e tim e, however, rotation should be slow enough to prevent ex­

cessive loss of sulfate through the holes in the basket and also to prevent splashing beyond the confines of th e centri­

fuge of the hot liquor. A maximum speed of 150 r. p. m .

A CID SU P P L Y TA N K F ig u r e 2

Let it be considered th at all this heat is utilized in convert- ing water a t 2 0° C. to steam at 100° C. Each gram, of water vaporized will consum e 80 + 538.7 (latent heat of vaporization), or 618.7 calories.

56 209 56,209 calories per mol of sulfate are equivalent to - or

, . rm 426 X 454 2000 .

426 calories per gram. Ih e n gjg"7'x "454 X s T = gallons of water w hich m ay be evaporated per ton of sulfate produced.

One ton of sulfate of am m onia is the equivalent of 515 pounds of am m onia and 1912 pounds of 60° Bo. sulfuric acid. Allowing for loss of acid, it can be considered that one ton of sulfate requires one ton (2000 pounds) of 60° B 6.

sulfuric acid. A ton of this acid contains approxim ately 447 pounds or 53 gallons of water. T he difference between the 164 gallons of w ater which m ay be evaporated and the 53 gallons brought in w ith th e acid, or 111 gallons, is the quantity to be adm itted to the system as wash water.

Although this wash w ater should be hot as used, perhaps 80° to 90° C., and so enter the saturator a t som ething over 20° C., y et the recirculated w ater loses some of its heat in circulating from the saturator through the troughs, settling boxes, and centrifuge back to the saturator and enters the saturator at som ething below 100° C. These tw o diver­

gences from the assumed conditions can be considered as approximately balancing each other, leaving the result un­

changed.

If it is considered th at a centrifuge when loaded contains the equivalent of 250 pounds of dry sulfate, then each wring­

ing of a batch of sulfate m ay be washed w ith approxim ately 14 gallons of water. A s the centrifuge operator, however, need not be skilled, but rather m echanically trained to this operation, and as th e sulfate is not weighed into the centrifuge nor the wash water measured, this figure of 14 gallons serves merely as a guide. A ctually a careful check of conditions within the saturator m ust be m aintained. I t is very easy to admit too m uch water, requiring additional acid to keep up the acidity, and thus build up the quantity of liquor be­

yond the capacity of the saturator.

The quantity of sulfate as centrifuged wrould build up a cake 6 to 8 inches thick around th e inner periphery of the basket. D uring loading the centrifuge should be rotated

has been found satisfactory while loading, after which for drying purposes this speed should be increased to 350 r. p. m.

and maintained a t that speed for approxim ately 5 m inutes.

W ith an acidity of th e saturator of 7 per cent, the result­

ing sulfate crystals are very sm all. More rapid rotation of the basket than 350 r. p. m . packs the cake so tigh t as to render it difficult to remove. Because of a rotation of only 350 r. p. m ., however, the sulfate discharged from the centrifuge contains about 3 per cent of m oisture, necessi­

tating further drying, as b y the rotary drier shown in the diagram (Figure 1) to the less than 0.5 per cent allowed.

A cid Supply

Tower Distributing

M E A S U R IN G BOX F i g u r e 3

M a te r ia ls o f C o n s t r u c t io n

M uch of the equipm ent for such a plant can be secured on the m arket. T his is especially true of piping, fittings, and valves, and of the centrifuges, rotary driers, and conveying and elevating equipm ent. Som e of the remaining equip­

m ent, the settling boxes in particular, and even the satu- rators, m ight also be available. I t is believed, however, th at there are advantages in constructing the last-m entioned equipm ent, as well as the tower and troughs, in place a t the plant.

T he lumber for such equipm ent should all be of a good

[m m n u m m i m t m i m

« ÿ iiîi^ iiîiîîiiîiis îîc s ï» : i m m m m m m m m K l i m Ł i f f i m a a m i i j

Acid Distributing Bex^• ■Lutes

SECTIONS OF ABSORPTION TOWER F i g u r e 4

770 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 19, No. 7

grade of longleaf yellow pine free from knots. B o lt heads should not protrude above the surface of any face or siding to be covered w ith lead.

T he lead should be of the w eights indicated in th e de­

scriptions of the various individual pieces of equipm ent.

N o le— S h e e t lead is u su a lly d esig n a te d b y w eig h t a s 3 0 -p o u n d lead, 8 -p o u n d le a d , etc . A s lead w eig h s a p p r o x im a tely 6 0 p o u n d s per squ are fo o t per in c h o f th ick n e ss, it is o r d in a r ily con sid ered for w e ig h t d esig n a tio n s a s w eig h in g a p ou n d per squ are fo o t per */** »n ch th ick n e ss. T h u s, 8 - p o u n d lea d is 8/m or */• in ch th ick , 2 4 -p o u n d lead is *4/* i ° r */« in c h th ick , etc . T h ere is an ex cep tio n to th is, in th a t V i-in c h ieaci js k n o w n as 30- p oun d lead.

All joints or seam s should be burned and not soldered. All parts of lead to be burned, as w ell as the burning strips, should be scraped free of all foreign material and oxide to a silvery w hite appearance im m ediately prior to burning.

H oles should not be made in the lead sheets for holding such sheets in place, either tem porarily or perm anently. If a tem porary m eans of holding th e lead in place during con­

struction is required, straps should be burned to the face of the lining and th e sheets hung b y these. T hese straps m ay later be cut off.

E q u ip m e n t

T he equipm ent described here is for a plant having a ca­

pacity of 60 tons of sulfate of amm onia per 24-hour day.

A cid-Suppi.y T a n k — T he acid-supply tank m ay be as shown in Figure 2. W ith the dim ensions as indicated, the tank w ill hold sufficient acid for an 8-hour shift run.

T he lumber should be of southern longleaf yellow pine of “square edge and sound” grade. T he posts are mor­

tised into th e sill and cap timbers and the frame is rein­

forced w ith ’/ 4-inch tie rods as shown. T he floor planking is 3 inches, w hile the siding is 2 inches thick. T h e box is

lined w ith 16-pound lead and covered w ith 12-pound lead carried by iron pipe to w hich it is strapped as shown. .A v en t through th e cover and an acid overflow should be pro­

vided. Acid flow from th e tank is regulated by means of a hard lead plug and seat controlled b y th e rod and winged nu t arrangement as shown. T he acid level “tell tale” may be placed a t the tank or a t som e other point of vantage to i the operator. T he float is a sphere of 10-pound lead, 12 inches in diam eter. T his will float approxim ately half sub­

merged in the acid.

Me a s u r i n g B o x — Because of its shape, the measuring box (Figure 3) is generally called “piano box.” This is sim­

ply a sm all box constructed of 12-pound lead, with a par­

tition or diaphragm containing a series of holes one above th e other and ranging in diam eter from ' / a to 1 inch, incrcas- j

ing in increm ents of Vs inch on the diam eter. B y watching the flow of the acid through this diaphragm, while adjusting the tank plug w ith the w inged nuts, a rather fine regulation of flow m ay be secured.

For a flow of 2 ' / 2 tons per hour necessary for the pro­

duction of 60 tons of sulfate, the piano box should run "37i holes.”

Ab s o r p t i o n To w e r— In erecting the absorption tower (Figure 4) care m ust be taken to place the splash brick oi tower packing as shown to avoid “salting up.” The walls of the tower are built of acid-proof brick with a mortar of silicate soda w ith a filler. T his mortar is mixed in the approximate proportions of 200 pounds of the filler known by various trade nam es as acid-proof cem ent to every 700 pounds of silicate of soda. A sm all am ount of powdered barytes should be added to each batch, preferably b y the mason as used, to accelerate the setting up of the mortar. The quantity of barytes varies acco:ding to the consistency of the mortar

July, 1927 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 771

ELEVATION AND SECTIONS OF SATURATOR F i g u r e 5

but, to give an idea of the relative proportions, it m ight be regarded as a handful per pailful of mortar.

T he brick should be so laid up as to avoid through courses.

To accomplish this, “sp lits” m ay be used, but these should be kept a t a m inimum . T he bricks should be dipped into the mortar, which should be sm ooth and of the consistency of pancake batter, and no mortar should be placed w ith a trowel. In laying, the bricks should be hammered into place in order to get the interior of the wall tigh t regardless of irregularities in the w all faces. C ut bricks should not be used.

T he brickwork laid up each day in mortar should be thor­

oughly washed down w ith 60° Be. sulfuric acid a t th e close of th at d a y ’s work. All arches should be built around a form. W eep holes, three on each of tw o sides and tw o on each of the other tw o sides, are to be provided at the base of the tow er as shown. Leadwork m ay bo flanged to the brickwork as shown.

The purpose of the distributing box, supported b y the w alls of the tower as indicated in the diagram, is to distribute the acid over the w hole area of the tower. T he acid inlets to the tower from this distributing box should be luted to prevent escape of vapor fum es to the building. T hese fum es will then be carried ou t through the take-off to the atmosphere.

Sa t u r a t o r—T he lumber for the con­

struction of the saturator (Figure 5) should be southern longleaf yellow pine of "select structural m aterial” grade.

T he inside is lined w ith W in c h asbestos lumber and w ith 24-pound lead as shown.

All joints should be cut to fit and the bevels on bearing timbers should be so cut th at the 4 b y 10-inch lining planking has full bearing across the w hole beveled face. A ll bolts should be placed w ith care and countersunk so th a t th e heads of the bolts are either flush or sligh tly below

•‘»O* CENTRIFU GAL DRIER F i g u r e 7 SE C T IO N OF TROUGH

F ig u r e 6

FIfturo

July, 1927 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 773 the face of the timbers on the inside w alls of the tank. The

’/rin ch asbestos lumber is to be placed in sheets as large as possible w ith tigh t joints and secured to the w alls of the absorber w ith large-head roofing nails. T he lead lining should be so placed th a t there w ill be as few joints as pos­

sible. T he cover of this saturator m ay be either of cast iron or of wood, lead-covered. T he am m onia distributor may be of 30-pound lead w ith a wrougkt-iron pipe collar to reenforce the point of flange. T he ejector should bo of Duriron or equivalent material. T he steam nozzle should fit snugly through the floor of the absorber and be caulked tight w ith lead wool. T he steam line to this ejector should be of lead pipe to a point above the liquor level of the sat­

urator.

As shown in the sketch, there is provided on one side a

“level box,” which is open and b y m eans of w hich the level of the liquor in th e saturator m ay be noted. T his open box also provides an entrance to the saturator of the acid and of the return liquor.

Tr o u g h s a n d Se t t l i n g Bo x e s— B oth the troughs and settling boxes m ay be constructed of wood, lead-lined, with the lead protected by acid tile as shown in Figure 6. This tile may be held in place b y lead laps as indicated, bu t need not be liquor-tight. Its purpose is to protect the lead against mechanical wear b y m ovem ent of the sharp sulfate crystals and the raking of th e crystals w ith either a wood or m etal hoe. The lining m ay be of 16-pound lead, using 12-pound lead laps to hold the tile in place. T h e ou tlet gates for the settling box and th e chutes connecting the box w ith the centrifugal driers m ay be of copper.

Ce n t r i f u g a l Dr i e r— T he centrifugal driers m ay be the 40-inch engine-driven suspended type, as shown in Figure 7.

T h e steel cases should be lined on the inside 'with 8-pound sh eet lead. T he baskets should be of perforated copper w alls w ith top ring and bottom of bronze, and w ith reen­

forcing hoops of copper. T he bottom discharge is to be closed w ith a bronze cone valve w ith a copper sleeve around the driving shaft. T he liquor outlet should be a lead pipe burned to the drier lining. Such a drier is easily obtained on the market.

Mi s c e l l a n e o u s Eq u i p m e n t— T he rotary drier m ight preferably be of the steam -heated air variety, such as is m anufactured b y a number of concerns in this country.

T he conveyor belting should be of 3-ply center, 4-ply edge, w ith ’/s-in ch rubber cover on the carrying side. Troughing idlers should be spaced about 4 feet 6 inches on centers, w ith return idlers spaced about 10 feet on centers and top-guide idlers spaced from 20 to 30 feet on centers. T he drive pulley should be rubber-covered, while the take-up pulley m ay be plain w ith ball-and-socket protected screw. T h e conveyor to storage should be provided w ith a weightom eter and an autom atic self-reversing tripper for discharging the material autom atically to any predetermined point in the storage.

T h e P la n t

T his equipm ent m ight be assembled into th e plant as pictured in Figure 8 . Such a plant would be available for the production of either sulfate of amm onia or phosphate of amm onia w ithout alteration or for both at the sam e tim e w ith but slight alteration.

C h ro m iu m P lating—A N e w Aid to In d u stry 1

B y D . H . K illeffer, A s s o c ia t e E d ito r

M

dustrial alloys but only now comm ercially available as a pure metal. A s long ago as 1854, B unsen succeeded in elec- trodepositing chromium from solution, b ut nothing rem otely approaching industrial application of this remarkably useful metal came into being until w ithin a very few recent years.

It is one thing to form an electroplate of chromium and quite another to m ake such a coating sm ooth, adherent, and com­

mercially useful, as m any failures in the past have clearly demonstrated. T he u tility of present chromium coatings and the m ethods by w hich th ey are obtained form the sub­

ject matter of th is article. It is hoped that b y a careful consideration of facts th e m ystery and unfounded rumors so widely current m ay be som ew hat dissipated and chromium’s true place in industry more clearly defined.

P r o p e r tie s o f C h r o m iu m

The properties of chromium which make it particularly useful to industry are its extrem e hardness and resistance to abrasion, and its ab ility to w ithstand m any of the ordinary agents of corrosion, including oxygen at high tem peratures and superheated steam . N o t only does the m etal itself possess these properties to a remarkable degree, bu t a com­

paratively thin electroplate of it on an unresistant base m etal imparts these properties to the com bination to a useful extent.

Ha r d n e s s— T he hardness of chromium on M oh ’s mineral- ogical scale is stated as 9, which places it in the class of

1 Received F e b ru a ry 8 , 1927.

em ery and far above any other known m etal. This figure is n ot necessarily absolute, as the result of a test depends largely on the m ethod of determ ination used, bu t th e fact remains th a t chromium is harder than iridium and the hardest of steels. In electroplating it som e variations in hardness are possible according to the conditions of plating, b ut it is easily possible to realize its full hardness in a plate. One hears of tests m ade on v ery thin plates of chromium, over a soft base metal, which can be broken b y a file, but a sufficiently strong base supporting a reasonably thick film w ill show a hardness greater than m any gem stones, approaching th at of sapphire and ruby.

We a r a n d Ab r a s i o n Re s i s t a n c e— R elated to its hard­

ness, b ut n ot necessarily inherent in it, is chromium’s resist­

ance to wear and abrasion. E ven very thin films exhibit this property to a remarkable degree and m etal parts subjected to the destructive forces of sliding wear can have their lives increased m any fold b y protection w ith a chromium plate.

Such parts as bearings in autom otive engines, engravers’

plates, and fine gages have had their useful lives prolonged as much as four to eight tim es b y chromium films less than a m il in thickness.

Co r r o s i o n Re s i s t a n c e— Chromium is decidedly resistant to a variety of chemical reagents, bu t it is not a panacea for all ills. Perhaps no other field is so subject to misunder­

standings and m isstatem ents by the overenthusiastic as that of corrosion resistance. T he natural optim ism of som e one v itally interested in the success of a particular m aterial for this purpose n ot infrequently leads to such overstatem ents of the case and the possible user becomes so involved in half- truths of nothing more than nuisance value, th at facts of

774 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 19, No. 7 great im portance are overlooked. Some of th e «old guesses b y

the uninformed have led to nearly th a t situation w ith respect to electroplated chromium, and it is our intention here to dis­

tinguish as clearly as possible betw een its real usefulness and th e fantastic rumors w hich do nothing more than hide the truth.

Chromium is unaffected b y the ordinary atm ospheric agents of corrosion and retains a brilliant finish although exposed to rain, snow, and sea water. I t resists all ordinary acids except hydrochloric and sulfuric, and is unaffected by sulfur compounds generally, including hydrogen sulfide, sulfur dioxide, and those present in petroleum and rubber dough.

M olten zinc, tin and brass, amm onia, and th e industrial organic acids, except oxalic, do n ot affect chromium. Its resistance to lactic and acetic acids is valuable. I t is not discolored b y heating in air up to 300° C. and resists physical breakdown b y oxidation up to 1149° C. Its m elting point is 1520° C.

E arly chromium plates were unsatisfactory in their r e s i s t a n c e t o c o r r o s i o n possibly because of the diffi­

cu lty of m aking a firmly a d h e r e n t plate free from pinholes, a condition ob­

viated b y recent im prove­

m ents in m ethods of its ap­

plication. T he presence of pinholes is especially to be avoided in a plate on iron, as chromium is “ n o b l e r ” than iron and its presence tends to increase the speed of electrolytic corrosion of

iron w ith w hich it is in contact. In general, it is preferred for corrosion resistance to pu t th e chromium on top of a nickel or copper plate to insure protection of the iron and com plete adherence of the final protective coating.

C o n d it io n s o f P la t in g

T he m ethod of application of chromium electroplates is subject to a w ide difference in detail am ong th e various op­

erators. T he general principle upon w hich all commercial baths now are based is the u se of a hypothetical compound, chromium chromate. E very bath contains chromium in both th e trivalent and hexavalent forms and there is pre­

sum ed to be a compound betw een these tw o. T he plating operation consum es hexavalent chromium and this m ust be constantly replaced. In addition, the bath usually contains an acid such as boric, sulfuric, phosphoric, or hydrofluoric, which is neutralized b y part of th e trivalent chromium present. Som e operators add relatively sm all quantities of other m aterials to im prove th e throw ing power of the bath.

T he bath originally used b y th e Bureau of E ngraving and Printing contains CrC>3, 250 grams; Cr2(S0 ^ 3, 3 grams; and Cr20 (CC>3) 2, 7 grams, per liter. T his is a representative bath and is based upon Sargent’s form ula.2 On account of th e differences of opinion as expressed in numerous patents on the subject, it is im possible here to go further into the m atter of the com position of the baths used.

V ariations in the tem perature of plating have a profound influence on the character of the result. From a warm solu­

tion a bright, sm ooth deposit of great hardness is obtained a t a tem perature of 4 0 ° C. or higher. T his typ e of coating is too hard to be satisfactorily buffed and m ust be applied to a sm ooth undercoating or to a sm ooth buffed piece of work.

In plating printing plates a t th e Bureau of Engraving and

* T ra n s. A m . Eleclrochcm. Soc., 3 7 , 279, 479 (1 9 2 0 ).

Printing, such a coating is applied to a sm ooth nickel or steel base and any slightly “frosty” areas are later buffed b y the use of 00 em ery cloth on a rubber buffer. Several operators prefer to apply this sm ooth, bright coating, as it avoids finishing of the hard chromium layer and the under­

coating of copper m ay be buffed more easily to a smooth brightness. One operator prefers to plate from a cold bath (cooled by w ater coils) and to buff th e resulting gray plate w ith abrasive. T he contention is th a t the gray plate can be obtained w ith better adherence 011 ordinary iron work than th e bright one.

T he containers used for the plating bath are of various kinds. One operator uses lead-lined steel vats; another, stoneware jars set in w ater w hose tem perature can be con­

trolled; and a third, steel tanks w ith removable glass linings to prevent current leakage. In the last typ e no tight joints are m ade betw een th e glass plates forming the lining. Both

hydrogen and oxygen are evolved during the plating process and it is necessary to provide fum e ducts to lead them off t o ' prevent n a s a l irritation from the entrained liquor.

Chromium solutions gen­

erally have poor throwing power, and it is necessary either to im prove this by changes in the solution or to form the anode into the sam e general shape as the cathode to take this into account. One operator is able to im prove the throw­

ing power of his solution to such an exten t th at he can plate a parabolic mirror on the inside using a plane anode. Others form the anode to alm ost th e exact shape of the cathode if it is n ot practically a plane. T he anodes them selves are of the insoluble tjqre, and lead and steel, as w ell as chromium alloys, have been used for this purpose. One patent covers th e use of chromium anodes w hich are intended to replenish th e bath by dissolving in it.

T he current consum ption of this plating operation is dis­

proportionately large because chromium m ust be reduced from a valence of six to a valence of zero and hydrogen is deposited a t the cathode along w ith the m etal. The various operators have preferred current densities which are not all in com plete agreem ent b u t generally range from 1.4 to 20 amperes per square decim eter on the cathode. A t low current densities the cathode efficiency rapidly drops off and 4 to a amperes per square decim eter is considered b y many to be th e low est practicable lim it, although others operate con­

siderably below these values. Several inventors lay stress in their patents on the relative sizes of cathode and anode surfaces, and som e state th a t th e anode should be half the size, and have tw ice the current density, of the cathode.

Others use anodes of approxim ately the sam e areas as the cathode. Indeed, practice varies w idely among different operators and the only discernable uniform ity is in the use of similar plating baths.

T he work is prepared for plating b y several methods, de­

pending largely on th e use to w hich it is to be put and to som e exten t on th e tastes of th e plater. I t is essential that th e surface be sm ooth and clean and this is ordinarily accom­

plished by' buffing and electrolytic cleaning. For wear resistance, as on engravers’ plates, bearings, etc., and for resistance to heat as on autom obile valves and piping for cracking stills, th e chromium is plated directly on steel. It is possible b y careful cleaning to apply chromium directly C h r o m iu m is n o w b e in g e le c t r o p la t e d c o m m e r c ia lly

o n m a n y d iffe r e n t m e t a l b a s e s . I t is p r a c tic a lly t a r n is h - p r o o f a n d im p a r t s t h is p r o p e r ty t o a r t ic le s p r o te c te d b y it . I t s h a r d n e s s is c o n s id e r a b ly g r e a te r t h a n t h a t o f c o ld -r o lle d s t e e l a n d i t is c a p a b le o f in c r e a s in g t h e w e a r o f p a r ts s u b j e c t t o a b r a s io n se v e r a l fo ld . I t r e s is t s n i ­ tr ic a c id , a ir o x id a tio n a t h ig h t e m p e r a t u r e s , s a lt w a te r , s u lf u r c o m p o u n d s in p e t r o le u m , a n d a n u m b e r o f o t h e r c o rr o siv e a g e n t s . A lt h o u g h n o t a c u r e fo r a ll c o r r o sio n ills , i t p o s s e s s e s m e r it u n d e r m a n y c o n d i­

t io n s . I t s c o s t is c o m p a r a b le w it h o t h e r e le c tr o p la te d p r o te c tiv e c o a t in g s .