tioned by the 1905 referee are probably modeled, as Mr. Booker has said, after the Massachusetts law
"which was framed back in 1873 before we had experiment stations, when the idea was that only water-soluble materials were available.”
La b o r a t o r i e s, Sw i f t Fe r t i l i z e r Wo r k s, At l a n t a, Ga., a n d Wi l m i n g t o n, N . C.
A D D R L 5 5 L 5 .
C O A L A N A L Y S IS 1
B y N . W . Lo r d.
W ithin the la s t few y e ars the su b je c t of coal a n alysis has becom e of g re a t im p o rta n ce to m a n y lines of in d u stry.
The dem and fo r th e an a ly sis of coal has com e from a g re a t variety of sources and la rg e ly from those h a v in g little a c quaintance w ith chem ical m ethod s a n d th e in terp reta tio n of chem ical results. T h e chem ists, on the o th er hand, have been com pelled to ta k e such m ethod s as w ere fou nd a t hand, and the result of these con d ition s has been n o t a lto gether sa tisfa c to ry in m a n y w ays.
If we consid er so m ew h at in d etail the vario u s d eterm in a
tions m ade in th e la b o ra to r y in con nection w ith coal test
ing, it will be easy to show how m uch is com m ercial and how little w h at m ig h t be called scientific. T h e so-called a n a l
ysis of a coal is u su a lly a p ra ctica l test of p u rity of the m a
terial on a sm all scale, b u t i t also in vo lve s d eterm ination s which are supposed in som e w a y to in d icate th e n ature of the coal itself.
T o illustrate, suppose w e con sid er an o rd in ary sam ple of bituminous coal. I t m a y b e assum ed to consist, first, of an organic co n stitu en t com posed of v eg e ta b le residues m ore or less altered b u t retain in g traces of its original w ood y structure and com p o site ch a ra cte r and con tain in g a s an integral p a rt certain in organ ic com ponents. L ik e its source, woody fiber, it absorbs m oisture in d am p w eath er and gives it up in d ry w eather. T h e u ltim a te chem ical com position of this m aterial varies w ith th e e x te n t of th e alteration , as shown in the peats, lign ites and bitum inous and a n th ra cite coals, and also, in all p ro b a b ility, w ith the n atu re of the vegetation from w hich it has been derived. T h is extre m e ly complex and in defin ite m aterial m a y be called “ coal su b stance” for w a n t of a b e tter term . In tim a te ly m ixed with this are in organ ic substances, p ro b a b ly m echanically introduced w ith th e origin al v eg e tab le ddbris or else pre
cipitated b y secon dary reactio n s from circu la tin g w aters, 'these m ay be in the n atu re of c la y s or fine sand and also intim ately m ixed iron p yrites. I h a v e exam in ed sam ples of coal under th e m icroscope, in w h ich m icroscopic c r y s tals of p yrites w ere sca ttered th ro u gh th e m ass in sufficient amount to g iv e h igh p ercen tages o f su lp h u r in th e total,
1 R ead a t th e Illin o is F u e l C o n feren ce, U rb a n a , 111., M arch 13.
1909.
y e t in w h ich a superficial e xam in ation o f the coal itse lf p ra ctica lly show ed no p y rites to th e unaided eye. O th er m inerals m a y be p resen t in the sam e w a y , even such unusual co n stitu en ts as zin c blend, and, as Dr. H illebran d has show n, con sid erable p ercen tages of van ad iu m sulphide. T h e e x trem ely com p lex n atu re of the organic con stitu en ts th em selves m a y be in ferred from the v aria b le b u t som etim es v e r y large am ou n ts of su lp h ur th ey con tain, w ell show n in th e case of certain peats.
N ow in a d d ition to this base con stitu tin g the p rincipal p a rt of the sam ple s u b m itte d .to th e chem ists fo r analysis, i t has secon dly, m ore or less coarse a d m ix tu re of slate, c la y s and other rock-like m aterial occurrin g in connection w ith the dep osits o f coal and n o t p ro p erly sep arated in m ining, bone coal, and also streak s of cannel and other associated m aterials, coal-like in ch aracter, b u t differing n o ta b ly e ven in th e organic m aterial th e y con tain from the coal itself. T h e fa c t th a t m a n y of these in gredien ts on stan d in g or exp osu re to a ir ra p id ly a lte r b y absorp tion of o x yg en , evap oratio n , etc., m akes i t ap p ear th a t the p ro b
lem is still fu rth e r com plicated.
N ow som e of th e things th a t the users of coal w ish to kn ow and fo r w h ich th e y turn to the chem ical an a lysis in th e hope o f receivin g in form ation a re th e follo w in g: the h ea tin g p ow er of th e coa l; the a m o u n t of ash o r in organ ic m a tter le ft on bu rn in g th e c o a l; the n atu re of the com b us
tion of th e coal, w h eth er flam ing, sm oking, rapid, or slow ; th e gas-p rod ucin g q u a lity of the coal b o th as to yield a n d as to th e n atu re of th e g a s; th e n ature of the ash yield ed b y th e coal, w h eth er fu sible or n o t; the a m o u n t of su lp h ur the coal con tain s; th e cok in g q u a lity of the coal and th e p u rity o f th e cok e p ro d u ced ; and the p ossibilities of im p rovin g its q u a lity b y coal w ashing.
In a d d ition to th e a b o v e are m a n y qu estion s of special ch aracter, such as th e n ature of th e coal substan ce, the relation o f its com position to the p reviou s geological his
to ry of the deposit, and the relation of to ta l h eatin g pow er to th e h e a tin g pow er a c tu a lly a va ilab le fo r techin cal operations.
W h a t are th e a n a ly tic a l m ethods a t p resen t used in the la b o ra to r y to m eet this series of qu estion s and to handle this v e r y co m p lex m aterial? M ost of th e la b o rato ry w ork is done upon a sam ple w h ich represents or is intended to represen t the a ve ra g e com position o f th e m aterial and w hich in no w a y recognizes th e sep arate con stitu en ts of the v e r y com p lex m ineral a g g re g a te of w h ich i t p u rp orts to be an a verage. T h e m ethods therefore g iv e results o n ly a p p ro x im a te ly related to th e coal su bstan ce and difficult of general ap p lication.
W e h a v e a s of gen erally recognized im p o rtan ce th e u lti
m a te analysis- as ord in arily m ade, g iv in g th e d eterm ination o f the hyd ro gen , th e carbon, the n itrogen a n d th e sulphur and th e percen tage o f ash le ft a fte r burning. T h is an a ly sis also includes an e stim ate of th e o x y g e n b y difference, w hich is of course o n ly a p p roxim ate, and has been fre q u e n tly pointed o u t in discussions of the su bject. T h is u ltim a te a n a lysis is c ap a b le of a high degree of a cc u ra c y fo r certain elem ents, w h ich I th in k cou ld be sa fely stated as w ithin 0 .0 5 per cen t, in th e case of hyd ro gen and perhaps 0 .3 p e r c e n t, on carbon , 0 .0 3 per cen t, on th e nitrogen and 0 .0 5 on th e sulphur. I do n o t m ean th a t closer re
su lts are n o t ob tainable, b u t o rd in ary w o rk in th e la b o ra to ry b y com p eten t chem ists would, I thin k, run w ithin
T H E J O U R N A L O F I N D U S T R I A L A N D E N G IN E E R IN G C H E M I S T R Y . May, 1909
these lim its. T h e valu e of the u ltim a te analysis in all tech nical ap p lications of the coal consists in its givin g a reason
a b ly a ccurate basis fo r the calculation of products of com bustion and for com parisons w ith the heating pow er of the coal otherw ise determ ined. T h e w eak est point in the u lti
m ate analysis is the u n certa in ty of its connections w ith the actu a l com position of the organic m aterial as d istin ct from the im purities. Carbon, hyd rogen and sulphur are present occasion ally as carbonates, as com bined w a ter and as su l
phates, respectively, in the slates and other m echanical adm ixtu res, and the u ltim a te an alysis does n ot distinguish betw een such occurrence and th a t in the coal substance.
Ingenious efforts to elim inate these uncertainties a s a ffect
ing th e heating pow er b y exam in ation of various sam ples of the sam e coal differing w id ely in percentage of m echan ical im purities h ave been m ade b y several chem ists.
In addition to the u ltim a te analysis, w e h a v e the m ore com m only m ade “ p roxim ate a n alysis,” consisting of the determ ination of the m oisture, ash, fixed carb on and v o la tile com bustible m atter in th e coal. M uch has been w rit
ten in regard to these determ inations.
O n the sam e sam ple of coal closely agreeing results can be ob tained on th e ash and fa irly close on the m oisture. T h e variation s in the volatile com b ustib le is m uch larger and can on ly be k e p t w ithin reasonable lim its b y v e r y careful adherence to a defined m ethod of procedure. T h e term m oisture sim ply m eans the loss in w eigh t under fixed con ditions of treatm ent. I t is intend ed and does bring the m aterial to a condition w hich can be du p licated closely and represents a fixed basis for com parison, bu t in no wise stands for all the w ater in the coal. T h e vo la tile com bustible, as has been carefu lly in vestigated b y Professor Parr, is b y no m eans properly nam ed. O n ly a fraction , and a v ariable fractio n a t th at, depending la rg e ly on the kind of coal, is com bustible, and a considerable fraction , consisting of w ater vapor, carbon dioxide, nitrogen and other diluents is in ert or non-com bustible. I t is well to recollect th at the proxim ate analysis of coal w as devised m an y years ago, and prim arily as a m eans of testin g the am ou n t of coke le ft b y coal. T h e vo la tile com bustible has since been the su bject of m uch discussion and m an y atte m p ts h ave been m ade to correlate it w ith heatin g valu e, geological changes and the various questions arising in coal u tilization . Som e undoubted connections h ave been shown, b u t I feel th at possib ly too little recognition has been given to the em pirical and m ore or less uncertain n ature of the determ ination.
O f grow ing im portance, p a rticu la rly in connection w ith coal washing, and as a m eans for the stu d y of coal samples, is the application of the separation b y g r a v ity or th e so- called “ float and s in k ” tests, in w h ich the coal crushed to a m oderate degree of fineness is separated on solutions of high specific g ra v ity , chloride of calcium for specific g r a v i
ties up to 1 .3 5 and chloride of sulphate o f zinc for higher specific gravities. Chloride of zinc solution can be m ade of a specific g r a v ity as high as 2 and b y dilution a n y -of the interm ediate gravities can be obtained. I h a v e used this m ethod in m y lab oratory for years to separate h e a v y m ineral m aterials like slate and p yrites, as prelim inary' to the stu d y of the com position of coal. T h e m ethod is excellen tly adap ted to tracing o u t the variation s in com position as the in te r
m ixed m ineral substances are elim inated. I t w ill enable the experim enter to distinguish w ith considerable accu racy
betw een the in heren t in tim a te ly m ixed ash and sulphur com pounds and the coarser and m echanical con tam in a
tions.
In recen t y e ars th e lead ing fa c to r in the com m ercial v alu atio n of coals has becom e th e calorific valu e or heating pow er of the coal and to -d ay the m ost im p o rta n t dem and on th e la b o ra to ry is the d eterm ination of this. T h e w id ely exten d in g use of th e bom b calo rim eter is lead ing to new problem s for th e in ve stig a tio n of th e chem ists. H ere again the h eatin g v alu e of the sam ple is m odified m ore than by m ere dilution b y th e n ature of th e m ineral a ggregate. A s Mr. T u rn er and oth ers h a v e show n, the h eatin g v alu e is not en tire ly proportion al in a g iv en kin d of coal to th e residue le ft a fte r d ed u ctin g the ash and th e m oisture, b u t th a t there are facto rs depend in g on the influence of the in organ ic m a
terial. W ork of th is kin d is of g r e a t im p o rtan ce in order th a t the effect of ash, m oisture and p y rites on th e com m er
cial valu e of coals m a y be m ore a cc u r a te ly know n.
C alo rim etry dem an ds con sid erable train in g and experi
m ental skill and the re cen tly ad op ted p o licy of the Bureau of S tan d ard s of furn ishin g m aterials of k n ow n heating v alu e so th a t th e con stan ts a n d correction of th e calorim eter can be determ ined is g r e a tly to be com m ended. T h e possi
b ility of error in calorim etric d eterm ination s d u e to altera
tion of sam ples should be borne in m ind. A v e r y fin ely pul
verized coal sam ple w ill ox id ize in m a n y cases v e r y rapidly, and co m p a ra tiv e results b y d ifferen t chem ists on such a sam ple are lia b le to be v e r y u n sa tisfa cto ry unless all made a t a p p ro x im a te ly th e sam e tim e on sam ples th a t h a v e been sealed in a ir-tig h t receptacles. E x p erim en ts m ade b y the F u el T estin g P la n t afford a m p le evid en ce of th e e x te n t to w hich this a ltera tio n m a y ta k e place.
T h e d eterm ination of th e w a te r e q u iv a len t of the calorim eter exp erim en ta lly g iv e s rise to m a n y difficulties and hence, e x c e p t for those h a v in g had a g re a t deal of expe
rience in fun d am ental m easurem ents, i t is fa r b e tter to use the calorim eter a s a c o m p a ra tiv e in stru m en t and depend fo r its con stan ts upon burn in g su bstan ces of kn ow n calo
rific v alu e such as are furnished b y th e B u rea u of Standards.
Com m ercial chem icals are qu ite v aria b le and differen t sam
ples of n ap h th alen e, ben zoic acid , etc., from d ifferen t dealers w ill differ n o ta b ly in th eir h ea tin g valu e. R e ce n tly the w riter has ob tain ed v e r y successful results b y th e m ethod of m ixtu res, ad d in g h o t w a ter to th e calo rim eter from the D ew ar flask or therm os b o ttle in w h ich i t is possible to read w ith g re a t a cc u ra c y the tem p eratu re of th e added water and to add th e w a te r to the calo rim eter w ith o n ly a very sm all correction fo r radiation loss d u rin g th e add ition . The m ethod has proved successful in the han ds of stu d en ts who h a v e m ade a num ber of w a te r e q u iv a le n t determ inations agreeing w ith in a v e r y sm all lim it of error w ith the calibra
tion of th e calorim eter ob tain ed in oth er w ays. O f course, this m eth od has the a d v a n ta g e of bein g a b so lu te and not relative.
T h e foregoin g ou tlin e has d e a lt w ith the la b o rato ry side of th e question. A ll th e a n a ly tic a l w ork, calorim etric w ork and e v e ry th in g else in con nection w ith the testing depend s fo r its econom ic v alu e on the fu n d a m e n ta lly repre
se n ta tiv e n ature of th e sam ple of coal tested in the labora
to ry. H ere is th e w e ak e st p o in t in the com m ercial appli
catio n of th e results. C oal sam p lin g is a m a tte r now promi
nent before the techn ical w orld. N ow th a t the extending
A D D R E S S E S . 3°9
recognition of the valu e of la b o ra to ry w ork is lead ing to the purchase of coal on chem ical specification s the w hole question of sam p lin g is under review . In g red ien ts m ost affected b y sam p lin g are o b v io u sly m oisture, ash, sulphur, and calorific valu e. I n a recen t p ap er of g re a t in terest Mr. E . G. B a ile y has presented a large num ber of results in which he criticizes e xistin g m ethods and la y s dow n certain general d ed u ction s from c a re fu lly co n d u cted e x p erim en ts a s to the gen eral p rinciples in v o lv e d in the securing of co rrect sam ples. Mr. B a ile y has, in m y opinion, done a v e r y v alu ab le piece of w o rk both in callin g a tte n tio n to the im p o rtan ce of the su b ject and in th e exp erim en ts th a t he has b ro u g h t forw ard. A s h a v in g been con nected w ith th e g o vern m en t work a t S t. Louis, I feel called upon to co rrect certain m is
apprehensions in regard to th a t w ork w hich I th in k h a v e unin ten tionally on his p a rt led him to place in a so m ew h at false lig h t as to the a ccu ra cy w ith w h ich the sam plin g w’a s done. A s I follow1 his p ap er he m akes a fu n d am en tal a s sum ption th a t the v aria tio n s in the p ortions of coal taken at the p la n t from th e sam e car sh ipm en t and sen t to th e Boiler, the G as P rod u cer and B riq u ettin g and W ashin g Plants were id en tical in com p osition w ith th e car load sa m ples and th a t th e v aria tio n s show n in these d ifferen t por
tions w ere due to v aria tio n s in sam p lin g of the p ortions a t the various plants, w hereas, the fa c ts of the case are th a t the differen t p ortions ta k en from the ca r w ere n o t supposed to be sam pled from the ca r b u t sim p ly p ortions unloaded at different points, and the reason w h y a n alyses w ere m ade of the sep arate p ortions w as because it w as recogn ized th a t the car load w as n ot u niform as fa r as con ten ts of ash, su l
phur, etc., w ere concerned, and th a t th e c a r load a n a ly sis could n ot be tak en for the differen t portions w ith o u t a pre
lim inary thorough m ix in g o f the w hole car load, w hich w as not p ractical. T h is is c le a rly stated on page 284 of P ro fessional P a p e r 48, P a rt 1, from w hich I qu ote:
I t w as in ten d ed t h a t th e c a r sam p le should represent the average of th e w h ole car, w h ile th e other sam ples stood for different p ortio n s o f it. T h e se w ould a v e ra g e a b o u t 5 tons each. In som e cases th e car sam p le w a s tak en on o n ly a p art of a car. T h e large v a ria tio n in th e d ifferen t sam ples in a few cases show's th e irr e g u la rity in th e coa l in th e car.
Experim ents w ere m ade a t S t. L o u is and published in this same w ork, g iv in g th e a n a ly sis of d u p licate sam ples, and while the results w ere n o t v e r y sa tisfa cto ry and some errors were found, th ey w ere n o t of the m agn itu d e g iv en b y Mr. B aile y from his com parison of th e other sam ples based
Experim ents w ere m ade a t S t. L o u is and published in this same w ork, g iv in g th e a n a ly sis of d u p licate sam ples, and while the results w ere n o t v e r y sa tisfa cto ry and some errors were found, th ey w ere n o t of the m agn itu d e g iv en b y Mr. B aile y from his com parison of th e other sam ples based