Oct., 1914
T H E JOCRNAL OF INDCSTRIAL A N D ENGINEERING CHEMISTRY
a double salt. I n a n y case i t appears t o be necessary t o work in acid solution in order t o prepare a stable salt, or mixture of salts, of t h e fertilizer constituents. T h e correct strength of alcohol a n d many other details would have t o be worked out. Another interesting feature is t h e per cent of water in t h e alcohol distilled off. Does t h e calcium sulfate form hydrate itself a t t h e expense of t h e water in dilute alcohol? T h e answer t o this question would depend on t h e range of existence of calcium sulfate di-hydrate in contact with alcohol of various concentrations, a t t h e temperature worked with; also on t h e vapor pressure of mixtures of phosphoric acid a n d alcohol. I t is, of course, presumed t h a t t h e original calcium phosphate is nearly d r y , or a t least contains no more water t h a n can be absorbed b y t h e sulfuric acid used. T h e points involved would require a good deal more investigation t h a n t h e writer has time for. A laboratory trial showed t h a t t h e resulting calcium sulfate was not hydrated t o t h e extent of t w o molecules of water t o one of calcium sulfate. Though calcium sulfate is so a b u n d a n t in nature, especially in the arid regions of t h e far west, as t o have slight value, i t is extensively used for plaster a n d other purposes, a n d is mined in convenient places. It is possible t h a t t h e extremely fine grain of t h e calcium sulfate resulting from t h e production of phosphoric acid, together with t h e accessible places a t which i t would be prepared, would give i t some commercial value. T o t h e advantages set forth m a y be added t h e fact t h a t t h e alcoholic solutions are easy t o filter a n d less corroding on t h e filters t h a n aqueous phosphoric acid. Of course there would be some loss of alcohol which would escape recovery. B u t with the advance of chemical technology, i t is believed t h a t these losses can be minimized. Evaporators designed for removing volatile solvents are becoming very common. L41coholis tending t o become cheaper rather t h a n dearer. Especially if t h e manufacture of plaster is combined with t h a t of phosphoric acid, the problem would be simple, as t h e heating of t h e residue t o bring i t t o t h e right s t a t e of hydration would, a t t h e same time, make recovery of t h e alcohol possible. As a last resort, t h e fuel value of t h e alcohol might be utilized b y drawing t h e draft for the boiler fires over i t , with appropriate devices t o prevent back firing or ignition of t h e possibly explosive mixture of air a n d alcohol vapor. As a denaturing agent for t h e alcohol, pyridin would probably serve best, as only a n exceedingly small per cent (which would, in no way, interfere with t h e reactions) is necessary t o give t h e alcohol such a n odor a s effectually t o prevent t h e consumption of i t for a n y purpose other t h a n t h a t intended. All t h e foregoing is intended t o be merely in t h e nature of suggestion. T o work o u t all t h e problems involve d , physic a 1-chemic a1 a n d technic a1. would re quire much time, a n d in so far as t h e technical features are concerned, special facilities. However, t o test t h e ease of extraction of t h e phosphoric acid b y alcohol, t w o experiments were made, each on one hundred
grams of calcium phosphate. t h e following composition:
829
T h e material used had Per cent
PiOa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37.6 CaO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5 Undetermined (by difference), . . . . . . . . . . . . . . 5 . 7 100.0
I-The one hundred grams of phosphate (after being treated with t h e sulfuric acid of j o o BaumC) were extracted with 9 j per cent alcohol, using a large Buchner funnel. After drying in a vacuum over sulfuric acid, t h e residue amounted t o I 0 j . j grams a n d contained 0.3 of one per cent of P206, amounting t o a n extraction of 99.2 per cent of the PnOs. E X P E R I M E K T 11 was t h e same except t h a t j o per cent alcohol was used for t h e extraction. T h e residue was 106.0 grams a n d contained 0.6 per cent P ~ O S , giving a n extraction of 98.7 per cent. hTo particular significance is t o be attached t o these small differences in extraction, except possibly t h a t t h e stronger alcohol as i t penetrates t h e mass with extreme readiness, extracts t h e phosphoric acid a little more thoroughly. With t h e strong alcohol especially, t h e extraction works with great ease and rapidity a n d from this point of view a t least, t h e use of strong alcohol is advantageous. EXPERIMEST
BUREAUOF SOILS, WASHlNGTOK
THE ACTION BETWEEN CLAY FILTERS AND CERTAIN SALT SOLUTIONS’ By W. B. HICKS Received June 5 , 1914
Colloidal suspensions such as are obtained when soils a n d clays are extracted with water pass readily through t h e best grades of filter paper, b u t yield perfectly clear filtrates when filtered through Pasteur-Chamberland or other close-grained porcelain filters. I n many cases, however, this t r e a t m e n t changes t h e composition of t h e solution. Briggs2 has shown b y titrating t h e chlorine t h a t no change in concentration occurs when S/’IOOO solutions of sodium chloride are passed through clay filters. By titrating t h e alkalinity t h e same investigator observed no change in N / 2 0 sodium carbonate a n d bicarbonate solutions, a decrease of 2 per cent in N/’Ioo, a n d a diminution of I j per cent in L ~ ~ / I O O O sodium carbonate solutions. By conductivity measurements he found a slight decrease in concentration in t h e first j o cc. fraction on filtering N , / ~ o o osolutions of a number of salts. Sullivan3 observed t h a t clay filters absorb about 18 per cent of t h e iron from N I ~ o o oferric sulfate solutions without absorbing a n y of t h e SO4 radicle. H e noted t h a t other bases go into solution, b u t in quantities insufficient to account for t h e iron absorbed. T h e results of these investigators show t h a t clay filters retain very little or none of t h e acid radicle, b u t m a y retain considerable quantities of t h e base when salt solutions are passed through t h e m . However, i t was t h o u g h t necessary t o repeat some of Briggs’ work in order t o determine whether such filters are 1 2
3
Published b y permission of the Director of the U. S. Geological Survey. U. S. Dept. .4gr., Bur. Soils, B d i , 1 9 , 1902. Econ. Geoi., 3 (1908). 754.
T H E JOURiVAL 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
830
uniform in their behavior during filtration. A t t h e s a m e t i m e a more extended investigation of t h e s u b ject was considered desirable. It seemed i m p o r t a n t t o know t h e composition of t h e filters, how much t h e y a r e dissolved b y salt solutions a n d t o w h a t e x t e n t t h e y become “salted” a n d t h e r e b y c o n t a m i n a t e a succeeding solution filtered t h r o u g h t h e m . Answering these questions experimentally a n d t h u s obtaining a more definite idea concerning t h e action between clay filters a n d salt solutions led t o t h e experimental results here presented. I n t h e experiments ordinary 8 in. P a s t e u r - C h a m b e r l a n d water filters were used. These showed o n analysis t h e following percentage composition: SiOz.. . . . 58.70 CaO . . . . . . 0 . 3 9 NazO.. . . . 0 . 4 0 AlaOa.. . . 39.20
MgO . . . . . 0 . 1 8
Kz0 . . . . . . 1.54
Total . . . . . . . 100.41
T h e filters were fitted with 2 0 0 cc. glass containers a n d ordinary side neck filter flasks. T h e y were cleaned b y washing i n t u r n with w a t e r , concentrated hydrochloric acid, a n d t h e n with w a t e r until t h e last washings showed only a slight opalescence with silver n i t r a t e .
Vol. 6 , No.
IO
T h e first series of experiments was carried o u t b y washing t h e filters with water until t h e washings were free f r o m salts, sucking air t h r o u g h t h e m t o remove a s much w a t e r as possible, passing t h e particular s a l t solution under investigation t h r o u g h t h e filter, discarding t h e first jo cc., a n d analyzing t h e filtrate. T h e solutions were prepared f r o m Baker’s analyzed chemicals, a n d were analyzed i n t h e s a m e m a n n e r a s t h e filtrates. T h e results are given i n T a b l e I. On s t u d y i n g these results i t will be observed t h a t filtration t h r o u g h porcelain clay filters produces n o change i n t h e boric acid c o n t e n t i n N / I O borate solutions a n d only v e r y slight changes-roughly a loss of 0.2 per cent-in N / I Osulfate solutions of t h e alkalies. W i t h chloride solutions, t h e loss i n concentration is slightly greater, a m o u n t i n g t o a b o u t 0.3 per cent i n N / I O a n d 0 . j per cent i n N / I O Osolutions. It will be f u r t h e r n o t e d t h a t t h e percentage loss i n chlorine corresponds t o t h a t of t h e t o t a l solids, indicating t h a t b o t h ions of t h e salt in question a r e retained b y t h e filter.
TABLE I-ACTION OF PORCELAIN CLAYFILTERS O N PURE SALTSOLUTIONS Cc. taken Change in Grams Cc. for RESIDUE concentration C1 by filtered analysis Grams Per cent titration ... 25 0.1777(a) .. .. 400 25 0.1773 -0.23 .. Filtrate from Filter 2 . . . . . . . . . . . . . . . . . . . . 400 25 0.1775 -0.12 .. N/10 KzS04-Original. ... 25 0.2175 .. .. Filtrate from Filter 1 400 25 0.2171 -0.18 .. Filtrate from Filter 2 400 25 0.2171 -0.18 .. N/9.84 NazB107-Original.. . . . . . . . . . . . . . . . 25 25.40 ( b ) .. .. Filtrate from Filter 1 . . . . . . . . . . . . .: . . . . . . 400 25 25.40 .. .. Filtrate from Filter 2 . . , . , . , , . , , . . , . , , . , , 400 25 25.45 .. N/10 NaC1-Original. . . . ... 25 0.1457(c) .. 0.6886 400 25 0.1453 -0.27 0,0882 400 25 0.1453 -0.27 0.0882 N/10 KC1-Original. ..................... 25 0.1864 .. 0.0887 Filtrate from Filter 1 . . . . . 400 25 0.1859 -0.27 0.0885 Filtrate from Filter 2 . . . . . 400 25 0.1860 -0.22 0,0886 100 0.0746 0.0355 400 I00 0.0742 -0:54 0.0353 400 100 0.0742 -0.54 0.0355 N/7.85 CaClz-Original 25 0.2179(d) 0.1128 Filtrate from Filter 1 . , , . , . . . . . . . . 460 25 0.2177 -0:09 0,1124 Filtrate from Filter 2 . . . . , , , , 400 25 0.2177 -0.09 0.1124 N/10 NazCOz-Original. . . . . . . . . . . . . . . . . . . . . . 25 0.1460(e) .. 400 25 +o: 62 .. 0.1469 Filtrate from Filter 1 400 25 +0.68 .. 0.1471 Filtrate from Filter 2 ... 25 0.1805 .. 400 25 0.1809 +0:22 .. Filtrate from Filter 2 . . . . ,, , 400 25 0.1810 +0.28 .. N/10.33 KzCOs-Original., 500 0.0361 .. Filtrate from Filter 1 . . . . . . . . . . . . . . . . . . . . 800 500 0.0387 +i:io .. Filtrate from Filter 2 . . . . . . . . . . . . . . . . . . . . 800 500 0.0397 +9,97 ..
SOLUTION N/IO NazSO4-Original
.....
( a ) On evaporation and ignition. ( b ) Titration with N/10 NaOH and Mannitol-Cc.
On evaporation and gentle ignition. ( d ) As sulfate.
(c)
T o o b t a i n a measure of t h e solvent action of water on these filters, 300 cc. of distilled water after passing t h r o u g h t h e m were e v a p o r a t e d , ignited a n d weighed. T h e results f r o m each of t w o filters g a v e 0.0013 g. or 0.0004 g. per I O O cc. T h i s was repeated, after passing 2 0 0 0 cc. of w a t e r t h r o u g h each filter, with a residue of 0.0003 a n d 0 . 0 0 0 2 g. per roo cc. T h e evaporation of 2 5 0 cc. of distilled water left a residue of 0.0002 g. per I O O cc. It is t h u s seen f r o m these results t h a t t h e solv e n t action of w a t e r o n these filters is very small. I n order t o determine w h a t changes t a k e place in a solution on passing t h r o u g h clay filters, t w o series of experiments were carried o u t : I-Pure salt solutions of known composition were allowed t o pass t h r o u g h t h e filters a n d t h e resulting change i n concentration determined b y analyzing t h e filtrates. 11-The q u a n t i t y of base retained b y a filter when a s a l t solution is allowed t o pass t h r o u g h i t was determined directly b y extracting t h e base with a different s a l t solution a n d analyzing t h e e x t r a c t .
Change in C1 Per cent
.. .. .. .. .. .. ..
.. .. ..
-0.45 -0.45
-0123 -0.12 -0157 -0.00
..
-0.35 -0.35
.. ,. , .
..
Alkalinity Change in Si02 Cc. N/10 HCI alkalinity Gram required Per cent
.. .. .. .. ..
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 0.0012 0,0013
.
0.6007 0.0009
,.
0.0617 0.0017
,. ,
.. ..
..
...
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
.. .. .. .. .. ..
...
..
..
..
..
.. ..
.. .. .. .. .. .. ..
...
2::oo
24.95 24.95 24.20 24.10 24.08 4.84 4.35 4.50
..
- 0:20 - 0.20 .. - 0.41 - 0.50 -10: 12 7.30
-
( e ) On evaporation as chloride.
However, we m u s t consider t h e f a c t t h a t t h e m a g n i t u d e of t h e changes with which we are dealing is quite small, a n d therefore t h e a p p a r e n t changes m a y be d u e , i n p a r t , a t least, t o errors i n analytical operations. At t h e s a m e t i m e t h e f a c t t h a t all t h e sulfate a n d chloride solutions examined show a distinct loss in concentration, points o u t clearly t h a t t h e filters d o retain a portion of these salts. N o calcium, a l u m i n u m , or silica could be f o u n d i n t h e filtrates, indicating t h a t these solutions h a v e very little solvent action on t h e filters. W i t h carbonate solutions of t h e alkalies, a s t h e chemical d a t a show, t h e results are s o m e w h a t different. T h e r e is a n a c t u a l increase in t o t a l solids determined a s chlorides a m o u n t i n g roughly t o 0 . 5 per cent in N / I O solutions, a n d 8 per cent i n N / i o o o solutions. Silica was e x t r a c t e d f r o m t h e filter i n quantities almost equivalent t o t h i s gain. Calcium was also f o u n d i n t h e ext r a c t . T h e alkalinity determined b y t i t r a t i o n with N / I O hydrochloric acid a n d methyl orange showed a slight diminution i n N / I Osolutions, a n d a b o u t 8 per cent decrease in N / ~ o o osolutions. This loss i n al-
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
OCt., I914
kalinity indicates a direct absorption of t h e salt or of free base. I n t h e second series of experiments it was a t t e m p t e d t o m a k e a direct determination of t h e q u a n t i t y of s a l t s retained b y porcelain clay filters. I n t h i s case t h e filters were washed with a large excess of t h e salt solution u n d e r investigation t o m a k e sure t h a t t h e m a x i m u m absorption h a d t a k e n place, a n d t h e n with distilled water until t h e washings were free f r o m t h e salt i n question. T h i s t r e a t m e n t presumably left t h e filters still containing only t h e q u a n t i t y of salt held so tenaciously t h a t water would n o t remove i t or a t most would remove i t very slowly. I n t h e case of chlorides t h e filters were washed until only a slight opalescence was shown with silver n i t r a t e i n zoo cc. of t h e filtrate; with carbonates, until no alkalinity could be detected. T h i s required f r o m 2 4 0 0 cc. t o 4 0 0 0 cc. of w a t e r , depending on t h e character a n d concentration of t h e solution. T h e salt which was still retained was t h e n washed o u t b y I O O cc. portions of a solution of iV 1 j a m m o n i u m chloride, until a negligible or c o n s t a n t residue was o b t a i n e d o n e v a p o r a t i o n a n d ignition. T h e various fractions were t h e n analyzed with t h e results given i n T a b l e 11. TABLE 11-SALTS EXTRACTED FROM FILTERS BY 100 Cc. PORTIOXS OF hT/5 NHlCl AFTER PRIORTREATMENT WITH: A-400 CC. 2 P E R C E N T KC1 AND THOROUGH W A S H I N G WITH W A T E R Combined filtrates Filter No. (200 cc. Water). . . . . . . . 1
RESIDUE(U)
I
Fraction 11... . . . . . . . . . 1
Gram Grams KC1 0.0010 o , o o l l ) 0.0007 0.0055 o,oo56} 0.0031 0.0020 o,oo20 0.0009
Fraction 111... . . . . . . . . 1
0.0014
Fraction I . . . . . . . . . . . . . I
Fraction I V . .
.........
B-1000 Cc. S,’lOO KCI (20Occ. Water).. . . . . . . . Fraction I . _ . .
1
o,oo14) 0.0011 o , o o l i ) 0.0008 0.0016
1 AND
.., 3
0.0015 0.0005
0.0006 0.0004
{ { { {{
Fraction 111... . . . . . . . . 3
0.0014 o,oolo
0.0035
0.0018
0.0009 0.0006
0.0005
0.0019 o,oo18} 0.0006
0.0004
o,oo2,}
1
0.0004
0,0009 (0.0009 0,0003 0,0003
{
.0002 { 00,0002
;:E{:
C-400 Cc. N/10 KzC03 A N D THOROUGH WASHINGWITH WATER Fraction1 . . . . . . . . . . . . . 1 0.0070 0.0009 o,oo64) 0.0033 0.0017 0,0009 Fraction 1 1 . . . . . . . . . . . . I 0.0017 0.0002 o,oo17 0.0009 0,0004 0.0002 Fraction 111. . . . . . . . . . . 1 0.0018 0.0002 ,,oo,9) 0.0006 0,0003 0.0002 Fraction I V . , . . . . . . . . . 1 0.0017 0,0002 o,oo,,} 0.0006 0.0003 0.0002 ( a ) All residues evaporated and weighed as chlorides.
1
of N / j a m m o n i u m chloride, a small a n d uniform q u a n t i t y being e x t r a c t e d b y succeeding fractions. Determined i n t h i s way, practically t h e same quantities of potassium a r e retained b y t h e filters from all t h e solutions t e s t e d , indicating t h a t t h e a m o u n t retained is independent of t h e concentration a n d character of t h e solution a n d possibly dependent only on t h e filters themselves. Moreover, t h e a m m o n i a similarly retained f r o m a m m o n i u m salts corresponds closely t o t h a t found T A B L E 111-AMMONIA EXTRACTED FROM T H E FILTERS BY 2 P E R CENT AFTER P R I O R TREATMENT W I T H 400 CC. O F hr/5 NHlCl AND THOROUGH WASHINGWITH WATER
Cc. 2 per cent KC1 Filter solution used No. 200 2 200 3 200 4
Cc. for titration N / I O equivalent 0.37 0.37 0.42
KCl
hTH3 Gram 0.0007 0,0007 0.0008
for potassium salts. I t t h u s a p p e a r s t h a t t h e filters become “salted” t o a small degree a n d c o n t a m i n a t e a succeeding solution filtered t h r o u g h th6m. A t t h e s a m e t i m e t h e t o t a l residue extracted b y a m m o n i u m chloride is much greater t h a n t h e potassium content even when considered a s t h e oxide or chloride, indicating t h a t a m m o n i u m chloride exerts a n appreciable solvent action on t h e filters. I n conclusion i t m a y be pointed o u t t h a t filtration t h r o u g h porcelain clay filters of t h e size here employed produces little or n o change i n t h e boric acid c o n t e n t f r o m b o r a t e solutions, a slight decrease i n concentration i n sulfate a n d chloride solutions of t h e alkalies, a larger decrease i n N / I Oc a r b o n a t e , a n d a considerable decrease in N / ~ o o oc a r b o n a t e solutions. I t m a y be observed f u r t h e r t h a t t h e filters become “salted” t o a slight degree during filtration, a n d also t h a t t h e y are appreciably dissolved b y solutions of a m m o n i u m chloride. Therefore, i t m a y be said t h a t t h e application of these filters depends o n t h e character a n d concentration of t h e solution t o be filtered. For moderately concentrated solutions a n d even for very dilute solutions of t h e chlorides a n d sulfates of t h e alkalies t h e percentage change, a s a rule, is very small. B y discarding t h e first portion, s a y I O O cc., of t h e filtrate, t h e liability of introducing a significant error can be much diminished.
t : ~ ~ ~ ~
{ 0.0002
4 Fraction 11... . . . . . . . . . 3
Fraction I V . . . . . . . . . . . 3
0.0004
Grams K Calculated 0,0002 0.0002 0.0008 0.0008 0.0003 0.0003 0.0003 0.0003
THOROUGH WASHINGWITH WATER )K ;;:: o,ooo5 o,ooo3 0 . 0002 0,0095 0.0095} 0.0025
, , ,
.
Grams K
83 1
{ { { {
T h e a m m o n i a similarly retained b y t h e filters f r o m solutions of a m m o n i u m chloride was removed b y washing with 200 cc. of a z per cent potassium chloride solut i o n , t h e filtrate being c a u g h t in dilute hydrochloric acid. T h e a m m o n i a was determined i n t h e filtrate b y t h e areometric m e t h o d after e v a p o r a t i o n t o small bulk. T o m a k e sure t h a t accurate results i n t h e estimation of a m m o n i a were obtained in t h i s w a y , several determinations o n known samples were m a d e , with a recovery of 99. j t o 100.j per cent. T h e results are given i n Table 111. As these results show, a small b u t appreciable q u a n t i t y of potassium is persistently retained b y t h e filters even a f t e r long washing with water. This is largely b u t n o t completely removed b y extraction with I O O cc.
U S GEOLOGICAL SURVEY WASKINGTON
SELECTIVE ADSORPTION By E. G. PARKER Received June 15, 1914
Adsorption, or sorption-a t e r m recently proposcdis most satisfactorily explained a t present as a concentrating of a solute a t a surface, whether t h i s concent r a t i n g effect is d u e t o differences i n surface tension or electrical potential. T h i s adsorption of solute from solution follows certain a r b i t r a r y laws, a new c o n s t a n t being required according t o t h e substance used, which furnishes t h e surface, t h e c h a r a c t e r of t h e surfaces of t w o different substances being a p p a r e n t l y never t h e s a m e . T h a t certain surfaces n o t only h a v e t h e power of adsorbing a solute a s a whole from solution, b u t also h a v e t h e power of absorbing a p a r t of t h e solute a t a greater r a t e t h a n t h e other, or of selectively adsorbing, can be shown qualitatively i n n u m e r ous ways. I n case of t h e selective adsorption of one ion of a n electrolyte a n accompanying or previous
