[P R E L IM IN A R Y PA PER ]
By Charles J. Moore, William H . Fry and Howard E. Middleton
B u r b a u o r S o il s , U. S. D e p a r t m e n t o f A g r i c u l t u r e , W a s h i n g t o n , D . C.
The stu d y of soil solutions an d th e aqueous ex
tracts of soils has engaged th e a tte n tio n of th is B ureau for some tim e p ast. In v estig ato rs in th is field have realized for a long while th a t th e aqueous ex tracts frequently contain considerable colloidal m aterial which renders th em opalescent, an d th a t it is q u ite im possible to clarify such solutions by any o rdinary means of filtration. V ery recently Anderson and P ry completed a prelim inary stu d y of th e solid phases obtained by th e ev ap o ratio n of certain soil extracts.
In order to o b tain sufficient m aterial th e y found it necessary to work up from 500 to 2000 lbs. of soil.
The am o u n t of colloidal m aterial obtained from so large a q u a n tity of e x tract was, of course, considerable, and it possessed such strik in g properties th a t some time was devoted to th e stu d y of it.
M E T H O D O F P R E P A R A T IO N3
A b a tte ry of b arrel-ty p e churns was used for stirring up th e soil w ith w ater. T w enty-five lbs. of soil were placed in each churn and 125 lbs. of pure distilled water added. T he churns were ro ta te d for several hours an d th e n allowed to rem ain a t rest for 24 hrs.
before th e su p e rn a ta n t liquid was siphoned off in to well-tinned m ilk cans. T he next step was to pass th e turbid liquid th ro u g h a Sharpies centrifuge. W hile this is a continuous process, it is calculated th a t each portion of th e liquid was subjected to th e force of 17,500 g rav ity for a t least 5 m in. T he liquid issuing from th e centrifuge was usually q u ite opalescent w ith colloidal m aterial, which was next sep arated from th e dispersing m edium by m eans of b a tteries of P asteu r- C ham berlain filter tu b es (Bogie F ). T he clear filtrate was co n cen trated in steam k e ttles for o th er researches.
The colloidal m aterial collected on th e outside of th e tubes in a slim y, stick y m ass w hich soon clogged th e filters. H ow ever, it was easily rem oved by blowing air into th e tubes. W e have given th e nam e “ u ltra clay” to th is m aterial.
The u ltra clay was purified in m any instances by dialysis. T his process proved very slow an d was finally given up, an d th e purification was carried out by stirring th e colloid up w ith distilled w ater and drawing th e w ater off by m eans of clean filter tubes.
This m ethod was very satisfactory.
C O M P O S IT IO N A N D P R O P E R T IE S
The chem ical com position of u ltra clay varies con
siderably. We are convinced th a t it is a m ixture of colloids, consisting m ainly of th e h y d ra te d silicate of alum inium , and containing v ary in g am o u n ts of ferric hydroxide, silicic acid, organic m a tte r, and possibly alum inium hydroxide. T here are alw ays p resen t small b u t v ary in g am ounts of calcium , m agnesium , potassium , an d sodium — w hether chem ically com bined
1 Received J a n u a ry 31, 1921.
* P ublished b y perm ission of th e S ecretary of A griculture.
* M eth o d developed b y R . O. E . D av is, L . B. O lm stead an d M . S.
Anderson.
or physically adsorbed has n o t y e t been determ ined.
W hen u ltra clay is suspended in w ater, it gives every evidence of being a tru e colloid. U nder th e ultram icroscope," it appears as d roplets of an am ber- yellow color and shows th e B row nian m ovem ent to a very m arked degree. W hen very d ilute solutions of electrolytes are allowed to diffuse u nder th e cover glass on th e slide, th e B row nian m ovem ent is a t once arrested. W hen suspensions are co n cen trated , m uch flocculation occurs. T he ad d itio n of an y electrolyte or of alcohol will, of course, have th e sam e effect.
W hen th e th ick mass is dilu ted or th e coagulating m aterial is rem oved by washing, a free suspension of th e colloid is again obtained. If th e colloid is very tho ro u g h ly dried on th e w ater b a th , it resuspends in w ater very slowly. The d ry m aterial is resinous an d of an am ber-yellow color.
C lay soils th a t have been tho ro u g h ly elu triated , as in th e m echanical analysis of soils, lose m uch of th eir p lasticity . T he u ltra clay, on th e o th er h an d , is very plastic when m oist, and exceedingly sticky. C er
ta in experim ents have been carried o u t to determ ine th e adhesive properties of u ltra clay. T he re su lts re corded in th e following tab le show th a t, up to 10 per cent, u ltra clay is a m uch stronger binding agent th a n Portland cement. However, th is is true only w hen the m aterial is dry. B riquets cem ented to g eth er w ith u ltra clay go to pieces very readily when tho ro u g h ly m oistened.
Cr u s h in g St r e n g t h o p Br iq u e t s
(B r iq u e ts 25 m m . h ig h a n d 25 m m . in d ia m e te r , m a d e u p w ith 18 p e r c e n t o f m o is tu r e u n d e r 1800 lb s . p re s s u re p e r s q . in . a n d d rie d a t 100° C .) C em enting
M ate rial
P o rtla n d Cecil S u sq u eh an n a C om m ercial
C em en t U ltra C lay U ltra C lay K ao lin
P e r cent K ilos K ilos K ilos K ilos
W ith Standard Grade o f S a n d as Used in Cement Testing
0.00 0.00 0.00 0.00 0.00
0 .5 0 0.00 3 .1 3 5 .4 2 0.00
1.00 0.00 7 .3 5 6 .7 0 0.00
2.00 0.00 1.3 4 8
5 .0 0 3 .2 3 61 .5 7 54^84 0 . 00
10.00 1 9 .1 6 122.52
W ith Q uartt Flour
9 6 .3 9
0.00 17 .3 8 17.3 8 17.3 8 17.38
0 .5 0 2 9 .8 6 3 3 .6 6 2 8 .0 8 17.56
1.00 4 4 .3 7 50.61 52 .3 2 19.40
2.0 0 7 2 .8 9 6 5.5 4 6 9 .7 0 17 .9 6
5 .0 0 8 5 .3 2 128.18 8 0 .6 8
10.00 112.30 3 0 4 .3 0 206 .8 2
I t seems evident, therefore, th a t u ltra clay is th e principal binding m aterial of th e soil, giving it plas
tic ity , cohesiveness, or hardness, according to th e m oisture co n ten t. T he recognition of these im p o rta n t properties shows th e fu n d am en tal relatio n th e m aterial bears to tillage an d to certain engineering problem s, including subgrades in road construction. T h e possi
b ility of finding a m eans to control certain of these properties offers a field of research-, w ith th e prom ise of results of economic im p o rtan ce to agriculture an d to engineering.
A B S O R P T IO N O F A M M O N IA
T h a t soils freely absorb gases is a very well-known fact, generally looked upon as a surface phenom enon, c h aracteristic to some ex ten t of all finely divided su b
528 T H E J O U R N A L OF 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. 13, No. 6 stances. I t seems ju st as reasonable to assum e th a t
th e a b so rp tiv e p ro p erties of soils are due to th e col
loids th e y co n tain , an d it was w ith th e view of dis
covering som e c h aracteristic p ro p e rty of colloids, n o t possessed b y th e o th er com ponents of soils, which could be m ade th e basis of a m eth o d for d eterm ining th e ir am o u n t in different soils, th a t th e following work w as u n d e rta k e n . U ltra clay was dried in an electric oven a t 110° C. for 24 hrs. I t was im m ed iately tr a n s ferred,w hile still h o t, to a Schw artz U -tube, an d weighed, a n d th e tu b e placed in a tra in of dry in g a p p a ra tu s.
T he S chw artz tu b e was th e n im m ersed in boiling w ater an d th o ro u g h ly e v acu ated w ith a n oil p um p. The U -tu b e w as next placed in an ice b a th , and d ry am m onia gas was passed over th e u ltra clay u n til it would a b sorb no m ore u n d e r a pressure of one atm osphere.
T he c u rre n t of gas was th e n sh u t offhand th e a p p a ra tu s was allow ed to s ta n d for 1 hr. fra m ake sure th a t equilibrium h a d been reached, as show n b y a m an o m eter a tta c h e d to th e U -tube. T he n ex t step was to draw off th e am m onia an d collect it in a tra in of ab so rp tio n a p p a ra tu s filled w ith a s a tu ra te d boric acid solution.
W hen a good deal of am m onia h ad been draw n off, th e U -tu b e w as again placed in boiling w ater an d th e residual am m onia displaced w ith a c u rre n t of air.
T he am m onium b o ra te solution w as titr a te d w ith 0.1 N sulfuric acid, using m eth y l orange as in d icato r.
a m o u n t o f e x p o s e d s u r f a c e— A t th e o u tset it seem ed desirable to in v e stig a te to som e e x te n t th e influence on th e ab so rp tio n of am m onia of surface ac tu a lly exposed. F o r th is purpose u ltra clay o b ta in e d from Cecil clay loam was divided in to tw o p a rts.
One p a r t was carefully g ra n u la te d so th a t all th e p a r ti
cles would pass th ro u g h a 1-mm. sieve, an d th e o th er half was m ade in to cylindrical m asses u n d e r a pressure of 3000 lbs. T hese cylinders m easured 5 m m . in d i
a m e te r an d 5 m m . in height. T h ey were extrem ely c o m p act a n d p resen ted exceedingly sm ooth surfaces.
B o th sam ples were air-d ried an d oven-dried as above described. T he following resu lts were o b tain ed :
E a c h cc. of C ecil u ltr a c lay , g ra n u la te d , a b so rb ed 111.1 cc. N H j E a c h cc. of C ecil u ltr a clay, cylinders, a b so rb ed 110.3 cc. N H i
T hese v alues are averages of several in d ep en d en t a n d fairly closely agreeing d eterm in atio n s. T he h ard , c o m p act pellets a p p a re n tly absorbed am m onia as read ily a n d to p ractically th e sam e e x te n t as th e loose, in co h eren t m aterial. T he ab so rp tio n an d evolution of am m o n ia in no way d isin teg rated th e pellets.
s u s q u e h a n n a c l a y s o i l— Since th e com pactness
or looseness of th e m a terial m ade no difference, th e d e te rm in a tio n s on u ltra clay o b tain ed from Susque
h a n n a clay soil1 were m ade on th e g ra n u la te d m aterial only, a n d th e following resu lt is th e average of five good d eterm in atio n s:
E a c h cc. of S u sq u e h an n a u ltr a c la y ab so rb ed 93.05 cc. N H j 1 F o r th e sake of com pleteness th e m echanical an aly sis of th e S u sq u e
h a n n a c la y soil is a p p e n d e d :
D ia m e te r C o n v en tio n al W eig h t P ercentages
M m . N am es G ram s
2 - 1 F in e grav el 0 .0 0 0 0 .0 0
1 - 0 . 5 C oarse san d 0 .0 0 0 0 .0 0
0 .5 —0 .2 5 M ed iu m s a n d 0 .0 2 5 0 .5 0
0^25 - 0 . 1 F in e s a n d 0 .1 0 5 2 .1 0
0 1 - 0 . 0 5 V ery fine san d 0 .8 1 5 16.3 0
0 .0 5 - 0 .0 0 5 S ilt 2 .2 6 3 4 5 .3 0
0 .0 0 5 -0 C lay 1 .7 9 3 3 5 .9 0
In all of th e above d eterm in atio n s from 7 to 10 g.
of th e colloid were used, a n d th e volum e was calcu
la te d from th e w eight an d th e absolute specific gravity, w hich in th e case of th e Cecil was found to be 2.76 an d th e S usquehanna 2.64.
I t m ay be w o rth y of n o te th a t on th e whole the S usquehanna colloid proved to be a w eaker binding m aterial th a n th a t o b tain ed from th e Cecil soil, and th a t its ab ility to absorb am m onia was less, to roughly th e sam e extent.
e f f e c t o f h e a t— T he above resu lts show conclusively
th a t soil colloids possess a rem ark ab le capacity for absorbing am m onia. If th e o th er com ponents of the soil should absorb none, i t would be necessary only to d eterm ine th e cap acity of th e colloid an d of th e soil itself in order to calculate th e q u a n tity of colloid in a given soil. L ight would be th ro w n u p o n th e point in d o u b t by h eatin g th e colloid to a tem p e ra tu re at which its n a tu re is en tirely destroyed. T he Cecil colloid was selected for h e a t tre a tm e n t, because it could be read ily o b tain ed in very p u re condition. Later S usquehanna clay soil was tre a te d in practically the sam e m anner, except th a t in som e instances th e inter
m ediate te m p e ra tu re stages were slightly different.
T he h eatin g was carried o u t as follows: A large quan
t ity of pellets was m ade up as above described and placed in sixteen silica crucibles. T he crucibles were th e n p u t in to a large, specially con stru cted , auto
m atically controlled electric oven. T he tem perature was carefully checked b y m eans of a good pyrom eter.
A t th e end of 24 h rs.’ heatin g , tw o of th e crucibles were rem oved an d th e te m p e ra tu re was step p ed up to the n ex t higher stage an d m ain tain ed for 24 hrs., w hen the next tw o crucibles were rem oved. T his procedure was co ntinued to th e end. As soon as th e samples were rem oved from th e furnace, am m onia absorption d eterm in atio n s were m ade, an d th e following results were o b tain ed :
Cec il, Ul t r a Cl a y
T e m p e ra tu re , 0 C ... 110 265 374 559 754 1130 Cc. N H 3 ab so rb ed p e r cc.
collo id ... 11 0 .3 1 0 0 .8 8 0 .0 7 4 .1 5 7 .5 2.2 Su s q u e h a n n a Cl a y So il
T e m p e ra tu re , ° C . 110 190 265 374 522 673 844 1130 C c. N H 3 absorb ed
p e r cc. s o il 2 7 .7 2 5 .3 2 4 .8 1 9 .7 1 4 .9 1 3 .6 7 .4 1.4
T h e assu m p tio n th a t th e ab so rp tio n of am m onia b y soils is due to th e colloids th e y co n tain seems to be borne o u t b y th e above results. T here is evidence of progressive destru ctio n of colloids th a t is n o t con
nected w ith th e process of d eh y d ratio n , as will be shown la te r on. A careful m icroscopic ex am in atio n of the m aterial h e ated to 1130° C. show ed no evidence of fusion even on sharp edges. T here was some change of color a n d a very decided shrinkage.
c a l c u l a t i o n o f r e s u l t s— In th e lig h t of th e above results, th e following calculations seem to be justified:
S u sq u eh an n a u ltra clay, h e ated to 110°, a b so rb ed 93.0 cc. N H 3 S u sq u eh an n a clay soil, h e ated to 110°, abso rb ed 27.7 cc. N H 3 S u sq u e h an n a clay soil, h e ated to 1130°, a b so rb ed 1.4 cc. N H 3
D educting 1.4 cc. N H 3 absorbed b y m aterial, pre
sum ably n o t colloidal, from 27.7 cc. absorbed by the u n altered soil leaves 26.3 cc. absorbed by th e colloid of th e soil. T herefore, if th e p u re colloid absorbs 93.0 cc. N H j an d th e re is sufficient colloid in th e soil
Ju n e, 1921 T H E J O U R N A L OF 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 529 to absorb 26.3 cc. N H 3, th e colloidal co n ten t of th e
soil m u st be 28.3 per cent.
A B S O R P T IO N o r D Y E S T U F F S
T h a t filtra tio n th ro u g h soil clarifies w ater an d removes m any colored bodies from it has been known for a g reat m a n y years. I t seems v ery probable that soil colloids p la y an im p o rta n t p a r t in th is phenomenon.
A larg e n u m b er of experim ents were carried out w ith colored in o rg an ic an d organic su bstances w ith the view of te stin g th e ab ility of soil colloids to absorb them . I t w as fo u n d th a t u ltra clay rem oved from true solu
tio n n o n e of th e inorganic su bstances tested , such as salts of copper, cobalt, an d nickel, b u t th a t it was highly a b so rb e n t of organic dyestuffs. M any dyes were te ste d , a n d while th e . u ltra clay absorbed them in large m easure, in every in stan ce except one some factor developed th a t in terfered w ith th e quantitative esti
m atio n along th e line we wished to pursue, viz., th e placing of a weighed sam ple of u ltra clay in water con
tain in g a n excess of dye, th e coagulation and removal of th e colloid a fter a tim e, an d th e estim ation of th e q u a n tity of dye left in solution b y com parison with a sta n d a rd d ye solution. U sually a change of shade m ade such a com parison im possible. In our experience, m alach ite green oxalate proved to be best suited to ou r m eth o d , th u s confirm ing A shley’s experience in his w ork on clays. Ashley found th a t lim e decolorized th e m a la c h ite green b y com bining w ith th e oxalate rad ical a n d form ing th e insoluble calcium oxalate.
T his is to be expected in view of th e fact th a t the c a r
b o n ate rad ical is a p p a re n tly n o t able to combine w ith th e p e n ta v a le n t nitro g en a to m of th e quinone-like secondary benzene residue of th e dye, resulting in th e loss of th e quinoid s tru c tu re upon which th e color of th e d ye depends. T he w riters a tte m p te d to remedy th is difficulty by adding an excess of oxalic acid, b u t a n y ap p reciab le excess of th e acid over and above th a t req u ired to p re c ip ita te th e calcium altered the shade an d dim inished th e in te n sity of th e color. I t was found, how ever, th a t a considerable excess of sodium oxalate h ad no effect upon th e dye. A fter th e difficulty w ith th e calcium h a d been overcom e, v ariatio n s in the size of sam ples used w ith a co n sta n t in itial amount of dye show ed th a t a d istrib u tio n effect was playing a p a r t in d eterm in in g th e am o u n t of dye absorbed, as th e follow ing resu lts in d icate:
SUSQUBHANNA Ct,AY SOIL CECI!, Ul.TRA Cl.AY
W t. of Sam ple W t. of D ye
A bsorbed W t. of Sam ple W t. of Dye
Absorbed
G ra m G ram G ram Gram
0 .2 0.0 1 1 4 0 .1 0.0156
0 .4 0 .0 1 6 8 0 .2 0.0200
0 .6 0.0 212 0 .3 0.0264
0 .8 0 .0 2 5 0 0 .4 0.0312
All of th e above sam ples h ad been h eated for 72 hrs.
a t 265° C. A second series ru n w ith Cecil ultra clay h e a te d a t 110° gave sim ilar results.
I n th e n ex t series th e weights of th e samples ta k en were th e sam e as above, b u t in stead of adding a constant in itial am o u n t of dye, th e am o u n t added was such as to leave a n ap p ro x im ately co n sta n t q u a n tity in solu
tio n a fte r th e sam ple h ad absorbed all it would u nder th e conditions. T he following resu lts were obtained:
Su s q u e h a n n a Cl a y So il Ce c i l Ul t r a Cl a y
W t. of D y e W t. of D ye
W t. of Sam p le A bsorbed W t. of Sam ple A bsorbed
G ra m G ra m G ra m G ram
0 . 2 0 .0 0 7 6 0 .1 0 .0 1 0 6
0 .4 0 .0 1 5 0 0 .2 0 .0 2 1 2
0 .6 0 .0 2 3 4
0 . 8 0.0 3 0 4
T he above d eterm in atio n s prove conclusively th a t com parable re su lts can be o b tain ed only w hen cer
ta in conditions of dye co n cen tratio n are carefully observed.
d e s c r i p t i o n o f m e t h o d— A g ram sam ple is shaken up w ith 40 cc. of distilled w ater in a large te s t tu b e.
A 0.1 N sodium oxalate solution is th e n added u n til th e re is a slig h t excess over th e a m o u n t req u ired to p re c ip ita te th e calcium . T he tu b e is corked an d placed in a n end-over-end shaking m achine for 15 m in. to in su re com plete p recip itatio n . T he suspen
sion is n e x t tre a te d w ith a c e rtain sm all excess of 0.2 p er cen t m alach ite green solution. T he m ixture is m ade up to definite volum e (70 cc.) w ith distilled w ater, an d th e tu b e again placed in th e shaking m achine for 1 hr. F iv e cc. of norm al sodium chloride solution are now a d d ed to flocculate th e colloidal m aterial, a n d th e tu b e is centrifuged in a large m echanical a n a l
ysis m achine u n til th e s u p e rn a ta n t liq u id is perfectly clear. T h is liquid is com pared in a D uboscq colorim e te r w ith a sta n d a rd solution of dye to w hich hav e been add ed all of th e reag en ts co n tain ed in th e other.
Tw o com plete series of S u squehanna clay soil sam ples were h e ated as previously described u n d er a b so rp tio n of am m onia; in fact, th e sam ples for th is w ork were h e a te d in th e sam e furnace a n d a t th e sam e tim e w ith th e clay pellets in order to be sure th e con
ditions were exactly th e sam e. T h e dye ab so rp tio n d e term in atio n s were th e n m ade as above described, w ith th e following results:
Su s q u e h a n n a Cl a y So il
(1 g. of soil, w eighed a fte r h eating , w as used in all d e term inatio ns) T e m p .,
✓---W eig h t of
<•—F ir s t Series—'D ye A bsorbed--- »
/—Second Series—* A verage Loss of
A verage W t. of Sam ple
° C. 1 2 1 2 on H e atin g
110 0.0358 0.0360 0.0352 0.0358 0.0357 0.000
190 0.0344 0.0338 0.0344 0.0342 0.0342 0.003
265 0.0 20 0 0.0200 0.0203 0.0197 0.0200 0 .0 0 5
374 0.0194 0.0202 0.0204 0.0198 0.0200 0.010
522 0 .0 0.0194 0.0196 0.0195 0.055
673 0.0190 0.0185 0.0197 0.0197 0.0192 0.064
844 0 .0 0.0105 0 .0 1 1 1 0.0108 0.065
1130 0.0018 0.0015 0.0019 0.0019 0.0018 0.065
C alcu latio n of a m o u n t of colloid in S u sq u eh an n a clay soil fro m d a ta o b ta in e d b y d y e a b so rp tio n m eth o d :
S u sq u e h an n a u ltr a clay, h e ated to 110° C ., ab so rb s 0.1196 g. d ye S u sq u e h an n a c lay soil, h e ated to 110° C ., ab so rb s 0.0357 g. d ye S u sq u e h an n a c la y soil, h e a te d to 1130° C ., ab so rb s 0.0018 g. d ye
D educting th e 0.0018 g. dye absorbed b y m aterial, p resu m ab ly n o t colloidal, from 0.0357 g. dye absorbed by th e u n a lte re d soil leaves 0.0339 g. dye absorbed by th e colloid of th e soil. T herefore, if th e p u re colloid absorbs 0.1196 g. dye an d th e re is sufficient colloid in th e soil to absorb 0.0339 g. dye, th e colloidal c o n ten t of th e soil m u st be 28.3 per cent. T his is exactly th e sam e resu lt as was o b tain ed b y th e am m onia absorp
tio n m ethod.
C alling th e m axim um ab so rp tio n of am m onia a n d of dyestuff 100, an d expressing th e o th e r values as p e r
C alling th e m axim um ab so rp tio n of am m onia a n d of dyestuff 100, an d expressing th e o th e r values as p e r