I-VD USTRIAL A Y D ENGINEERING CHEMISTRY
746
water and the color resulting from same, is plotted from plant data for 1925. Since there is no relation between the trend of these curves it shows that the manganese is present as a combination of stable and unstable salts. Even after filtration soluble manganese will be present from such a supply. Upon addition of alkali to reduce pipe corrosion by water containing free carbon dioxide, this manganese is promptly converted to the hydroxide with production of color by o-tolidine. This condition will give higher readings for chlorine than actually exists and therefore indicate security from a chlorine residual test, when as a matter of fact the actual amount of free chlorine present may be negligible. Such a condition may easily exist in a small purification plant, with meager or no laboratory facilities, where greater reliance is placed upon the residual chlorine test than in the
Vol. 19, No. 6
larger ones under constant bacteriological control. To call attention to these possibilities is the object of this paper. Bibliography I-Buswell and Boruff, J . A m . W a t e v W o r k s Assoc., 14, 384 (1925). 2-Ellms and Hauser, J . Ind. Eng. Chem., 6, 553 (1914). 3-American Pub. Health Assoc., Standard Methods of Water Analysis, p. 59 (1925). 4-Smith, “General Chemistry for Colleges,” p. 620 (1920). 5-Taylor, J . Phys. Chem., SO, 145 (1926). 6--Theriault, U.5’. Pub. Health Bull. 161 (1925). 7-Scott, “Standard Methods of Chemical Analysis,’’ p. 302 (1918). 8-Dennis and Whittelsey, “Qualitative Analysis,” p. 58 (1902). g-wilborn, Farben-Zlg., 31, 338 (1926). l@-Bancroft, “Applied Colloidal Chemistry,” p. 175 (1921). 11-Anargyros, Comfit. rend., 161, 419 (1925). 12--Baylis, J . A m . W a f e r Works Assoc., 12, 211 (1924). 13--Robinson, Gardner, and Holmes, Science, 60, 423 (1919).
Adsorption of Vapors b y Ferric Hydroxide Gel’ By J . H. Perry 1211 DELAWARE AVE., WILMINGTON, DEL.
The eficiency
of the adsorption cjf fourteen
capors by ferric hydroxide gel has been studied by a dynamic method. preliminary data indicate that ferric hydroxide gel can be used f o r the recovery of most vapors ac. ejectiueh as alumina and silica gels.
T
HERE are in the literature considerable data on the
adsorption of vapors by the gels of silicic acid and alumina. There appear to be no such data, however, for a pure ferric hydroxide gel, although there are a number of papers on the adsorption of ions and dyes by this gel. The similarity of silica, alumina, and ferric hydroxide gels led to the belief that the last would have approximately the same efficiency of adsorption from vapor-air mixtures and approximately the same saturation capacities for different vapors as the first two gels. This paper describes results obtained in a general investigation of the adsorption of fourteen vapors by ferric hydroxide gel. General Procedure
PREPARATION OF GEL-C. P. ammonium hydroxide was added to a n aqueous solution of C. P. ferric nitrate. The resulting ferric hydroxide was then washed with hot distilled water until the washings showed no trace of nitrates. 1
Received January 20, 1927.
These
The washed precipitate was dried, first a t 60” C., at-which temperature most of the shrinkage took place; then a t 100” C. until a hard, glass-like material was obtained. This was broken up and screened. The material used for this series of experiments was 10-12 mesh. ACTIVATION-unless otherwise stated the gel was activated by passing through it dry carbon dioxide-free air heated to 230’ C., the gel being heated in the same bath as the air. During the cooling from 230” to 25” C. no air was allowed to come in contact with the gel until the vaporair mixture was started through it. This activation was repeated after each experiment, until the gel returned to its original weight, before being used in the adsorption experiments with another vapor. The duration of the activation varied but little after each experiment and was about 2 hours. ADsoRPTIoN-The general method of the experiments was the same as that described in a previous paper2 and consisted in passing a vapor-air mixture at a definite rate (50 cc. 2
Perry, J . Phys. Chem., 29, 1462 (1925).
June, 1927
I,VD USTRIAL A N D E,VGINEERIXG CHEMISTRY
747
ildsorpfion of N - B i + y I
and l s o b u f y l Alcohols
/
/p
4 / /
/
a
/'/
/
per minute) through a U-tube containing a known weight and known apparent volume of the activated gel, which was thermostated at 25' C . The process of the adsorption was followed by weighing the saturator tubes and the U-tube containing the gel at frequent intervals. The vapor-air mixtures were prepared by passing dry, carbon dioxide-free air through two spiral saturating tubes (Vanier type) slowly enough to assure saturation of the air steam The flow of air was controlled by a capillary flowmeter inserted in the line before the drying and carbon dioxide-removal tubes. A11 chemicals were of C . P. grade and were not purified further unless otherwise stated. The temperature in each eyperiment was 25 O C. Results
ADSORPTIVE POWER OF FERRIC HYDROXIDE C:EL AS i FUNCITSIv.4TER CONTENT-The adsorptive power O f a gel for vapor depends among other things upon its water content. Patrick and McGavack3 measured the adsorption of sulfur dioxide by silica gels containing varying amounts of water and obtained the maximum adsorption capacity with gels containing from 4.86 to 9.97 per cent of water. In agreement with these results, Miller4 has stated that the optimum water content of silica gel is from 5 to 7 per cent. Geldards found that the amount of water in alumina gel had no effect on its adsorptive capacity. Dover and Marden6 came to the same conclusion. ltIuiiro and T I O S OF
J . A m . Chem. S O L ,49, 946 (1920) Chem. & M e f . Eng , 23, 1155 (1920). 6 THIS JOURNAL, 17, 89 (1925) e J. A m Chem. S O L ,39, 1609 (1907). 8 4
6.36 13.56
21.16
3.67
3.24 2.4;
Unless otherwise specified, all experiments that follow were carried out using a ferric hydroxide gel containing 6.36 per cent of water. 7
THIS JOURNAL, 17, 58 (1925).
Vol. 19, KO.6
INDUSTRIAL A N D ENGINEERING CHEMISTRY
748
ADSORPTION OF PURE SULFURDIOXIDEAND PUREAMMOXIA alcohols, carbon tetrachloride and methylene chloride, ethyl THESEGASES FROM AIR MIXTURESOF EACH- and methyl alcohols, acetone, methyl iodide and ethyl broWith pure (100 per cent) sulfur dioxide and ammonia the mide, benzene, and gasoline. The saturation values for all adsorption curves (Figure 11) follow the complete adsorp- the vapors studied are given in Table I. tion line until the gel has almost reached its saturation Discussion of Curves capacity. It was therefore of interest to determine the adsorption efficiency curves for air mixtures of the gases. Munro and Johnson' give three types of adsorption curves obtained with alumina gels. The curves for ferric hydroxide gel may be classified in a similar way: AND OF
TYPEI-The adsorption efficiency is never 100 per cent and decreases continuously until the saturation value has been reached. The curves for chloroform, acetone, methyl iodide, and ethyl bromide are of this type.
Adsorption o f Mefhy/ Iodide and €fhy/ 6rom;de
These data are also shown graphically in Figure 11. The dotted line shows the curve of complete adsorption. I n each case the addition of air to the pure gas causes a marked lowering of the saturation capacity of the gel, which is in accord with the results obtained by Munro and Johnson for similar gas mixtures using alumina gel as the adsorbent.
f l q u i e Z7D '
O
4
Adsorpfion of Benzene Wt. of ge/ used = / 0 6 0 5 q r a / n s
W
ADSORPTIONOF WATER VAPOR-The adsorptive capacities of both silica and alumina gels are much greater for water than for any other substance so far studied. This is also true of ferric hydroxide gel. This gel adsorbs about 151per cent of its weight with 100 per cent efficiency, after which the efficiency slowly falls off from the complete adsorption curve until a saturation value of about 18 per cent of its weight is reached. Table I-Saturation
VAPOR Acetone.. Ammonia: Pure NHr ........... "*-air mixture.. Beqzene.. ............. Butyl alcohol (normal). Isobutyl alcohol.. ...... Carbon tetrachloride. , Chloroform.
............. ....
. ...........
50.9 4.36 3.5 10.1 29.4 21.3 33.3 36.0
e
4Gr0ms6V0p-3r
'.hpp/&
l4
TYPE11-In this type of curve the adsorption is 100 per cent efficient for some time and then proceeds to the saturation point, which is reached only after a long time. The adsorption of carbon tetrachloride, ethyl alcohol, normal and isobutyl alcohols, benzene, and gasoline is of this type. The first portion of the curve characterizing this type, where the adsorption efficiency is 100 per cent, is ascribed by Munro and Johnson to what Langmuir has called primary adsorption. The second part of the curve, where the adsorption gradually approaches zero efficiency, is ascribed to a combination of events-i. e., secondary adsorption, capillary condensation, and diffusion into the gel. I n the light of our present knowledge regarding adsorption and attendant phenomena this is probably as accurate a n explanation as is possible. Where the adsorption curve shows a sharp break, as in those of sulfur dioxide and ammonia (Figure 11), the causes of the secondary phenomena are for the most part absent. TYPE111-According t o Munro and Johnson this type of curve is due to a chemical reaction. Here the adsorption is never 100 per cent efficient. The curves proceed in a straight line until the saturation value is nearly reached. This type of curve is represented in these experiments by the adsorption of methylene chloride and methyl alcohol.
It should be noted that there is an initial lag in the adsorption curves of chloroform and isobutyl alcohol. No adequate explanation for this phenomenon has yet been suggested.
New Fabric to Wrap Wool Bales
Values
(Gel contains 6.3R per cent water)
GRAMSVAPOR PER 100 GRAMSGEL
F i g u r e ZX Adsorption of &soline
GRAMSVAPOR
PER 100 VAPOR GRAMSGEL Ethyl alcohol ......... 10.8 Ethyl bromide.. ...... 11.5 Gasoline.. . . . . . . . . . . . 6.7 Methyl alcohol. . . . . . . 10.2 Methyl iodide.. . . . . . . 12.6 Methylene chloride. , . . 28.2 Sulfur dioxide: Pure SOz . . . . . . . . . . 1 3 . 0 SO,-air mixture. . . . . 10.9
OTHERVAPORS-Adsorption data for the following vapors are given in Figures I11 to IX: Normal butyl and isobutyl
Wool merchants and textile manufacturers of the Bradford District in England have for some time past been working on a material t o replace jute fabric as a n outside wrapper for wool bales. A fabric has now been designed t o overcome the difficulties resulting when jute fibers get into the wool. The new fabric is composed of strands of paper twisted around a strand of unusually strong steel wire. The project has passed the experimental stage and will shortly be placed before the wool growers of t h e colonies for consideration. It is stated that this fabric can be manufactured in large quantities and at prices which compare favorably with the cost of jute. A representative of the British concern expects to visit the United States shortly t o interest American textile manufacturers.
