November, 1931
IlVD USTRIAL AND ENGINEERING CHEXISTRY
shown in Table I. Then a portion was vigorously stirred with 1 per cent of the negative catalyst and heated exactly as before. I n Table I the oil alone reached a temperature of 165.5' C. in 1 hour, dropped 10" in the next 15 minutes, and so on. It is considered that any oil which shows a temperature exceeding 100" C. in 1 hour or 200" C. in 2 hours is a dangerous oil and liable to produce spontaneous combustion. Applying this rule to the substanres in the table, i t is seen that resorcinol, orcinol, o-chlorophenol, benzaldehyde, nitrobenzene, oil of caraway, and cutch extract all give temperatures above 100" C. in between 1 and 2 hours. These, then, do not inhibit the reaction and are of no use as negative catalysts. On the other hand, hydroquinol, catechol, quinone, thymol, and Kos. 20 and 103 creosotes do not allow an appreciable rise of temperature and may be regarded as satisfactorily preventing the heating of the oil. The first ten tests (through oil of caraway) were made with one
1305
sample of red oil. As this was exhausted, the last seven tests were made with a new sample. How this behaved can be seen from the title "New oil alone." KO.20 creosote is a commercial product described as a blast-furnace oil (from blast-furnace tar) containing between 25 and 40 per cent of high-boiling tar acids. No. 103 creosote is a similar product, coming from a vertical-retort coal tar containing from 20 to 25 per cent of tar acids. From this it would seem that the addition of a very small quantity of commercial creosote oil would render any red oil absolutely safe for use. The amount added is not readily perceptible by the sense of smell. Inasmuch as this may become useful industrially, a patent for the use of phenols or negative catalysts with textile oils has been taken out ( 2 ) . Literature Cited (1) Gill, A. H., IND.ENG. CHEM.,16, 23 (1924) (2) Gill, A. H., U. S. Patent 1,791,057 (Feb. 3, 1931). (3) Swett and Hughes, J. IND. ENG CHBM, 9, 623 (1917)
Relative Concentrations of Negative Ions in Different Parts of an Electroosmose Edward Bartow and Floyd W. Perisho IOWASTATEUNIVERSITY, IOWACITY,IOWA
The removal of the negative ions-chloride, carbonBartow and Jebens (2, 3 ) , U R I F I C A T I O N of ate, and sulfate-is practically complete at all rates in 1930 c h e c k e d t h e w o r k water by electricity, in below 30 liters per hour from solutions up to 250 parts previously done, obtaining a which the c u r r e n t is per million. Bicarbonate ions are not easily removed water having a r e s i d u e of used as a source of heat, has from solutions of carbonate alone at rates in excess less than 15 p. p. m. from n o t b e e n economically sucof 25 liters per hour, but are quickly removed from the water supply a t the Unicessful. The use of the cursolutions containing sulfate or chloride ions. versity of Iowa, which has a rent to remove electrolytes The limit of the machine is reached at 500 parts per total residue of 725 p. p. m. from a central cell to cells conmillion chloride radical if the rate is in excess of 25 They suggest that less than taining the anode and cathode liters per hour. If water of only comparative purity one-half t h e e l e c t r i c a l has furnished a means of water is desired, rates of 35 and even 40 liters per hour may energy would be required to treatment by electricity that be practical even with water of high salt content. reduce the residue from 600 is apparently economically Partially purified water may be prepared also by the to 300 p p. m. than would be possible. The application of use of fewer cells and without the necessity of washing required to reduce it from this method-the electrocsthe last two cells with pure water. 300 D . D . m. to zero. mose process-to the purification of water was described T i e 'apparatus (Figure 1) for the first time in 1926 by Illig (7,8),who developed the proc- used in this study is the type I11 machine made by the ess in Berlin. Patin (10)in 1928continued the work and showed Elektro-Osmose A-G. of Berlin, with rated capacity of 25 that, under certain conditions, the preparation of pure water liters per hour. The objects of this study were: to ascertain the limits of by the electroosmose process is cheaper than distillation. Marie (0) in 1928 stated that salts are not entirely removed efficient removal by this apparatus of some of the common by the electrodsmose process, but that water may be made negative ions from solutions of different concentrations and a t sufficiently pure for most purposes. He lists as advantages different rates of flow; to obtain a picture of the progress of that the product is cold, the cost is less than distilled water, the reaction within the apparatus in order that the rate may be regulated to produce partially purified water of the desired its control is simple, and little attention is required. Behrman (,4, G) set the limits of the apparatus a t 1000 mg. degree of purity; and to study the effect that various ions in per liter and recommended the use of the process in purifica- a mixture have upon the removal of other ions. tion of water for making ice, advising that purification be not Theoretical Principles of Electroosmosis carried below 200 p. p. m. In the purification of water, the amount of material that may be left in may depend upon the The electro6smose principle is, in general, the principle of use to which it is to be put-for example, for use in boilers, electrolysis in which there is a separation a t the electrodes of laundries, and in industries requiring water of various degrees the ions of the solution or of the products of their discharge. of purity. Ions of the dissolved salt are drawn toward the electrodes together with the H + and OH- ions present in the water. 1 ReceiLed May 25, 1931. Presented before the Division of Water, Sewage, and Sanitation at the 81st Meeting of the American Chemical At each electrode the ion having the least decomposition Society, Indianapolis, Ind., March 30 t o April 3, 1931. potential is discharged and either appears in molecular form 2 Abstract from a dissertation submitted in partial fullilment of the or reacts with other ions present in the solution. This requirements for the degree of doctor of philosophy in the Department of Chemistry, State University of Iowa, by Floyd W Perisho. process is modified by the introduction of special diaphragms
1306
1NIjUS"RIAL A iz'D ENGINEERIhrC CIfEMISTR Y
Figure I-Elecrrob'srnoue Apparatus
Yol. 23,
xu
I1
Distilled water can be pumped into the solution storage, into the s o l u t i o n feed reservoir for eieming the apparatus, or into the elevated purified-water tank for washing the last two cells a t the beginning of a run before sufficient purified water has heen collected, By a similar arrangement the purified water can he pumped from purified-water storage tank into the solution storage tank or either of the overhead tanks. During the regular run the salt solutiori is pumped directly into the solution feed reservoir from which it flows by gravity to the elect~roijsmoseapparatus. Rate of Flow The rat,c of flow is governed by allowing the solution feed water to enter the apparatus through glass nozzles whose rate h a s becn previously determined. This makes it possibie to dupiicate any given rate for the succeeding solutions at any time. A uniform rate requires a constant head or uniform level of the solution in the solution feed reservoir. A float chamber (Fignres 1,2, and 3) is connected with the feed water reservoir by 1.25-inch (3.16cm.) pipe and a float connected witli an electric switch, as shoim in wiring diagram (Figure 3). I3y this arrangement the h e 1 of the solution i s kept constant within 3 inches (7.62 cni.), and the rate of flow quite uniform a t all times. The solutions are made by dissolving tlje proper amount of the salt under consideration in a sniall amount of distilled 7vat.er and slowly adding it to distilled water in the storage tank. In filling the machine, care is taken to keep the anode and cathode chamhers and the central cells at the same level by filling rsll at the same time and a t the same rate.
to prevent the reunion of the separated ions, together with a device for the constant removal, by mashing, of the products from the electrode chambers. Uehrriian (5) in 1929 indicated that the process is not simple electrolysis but is complicated by electroendosmosis, the movement of the water toward the cathode, and electrophoresis, the movement of colloids to the electrode conipartments. The anode and cathode are enclosed in separate compartments with a central cell beta,ccn them. The electrodes are connected with bus bars on the back of the apparatus. These are in turn connected with a d . e. generator furnishing 110 volts. I n the tests described in this paper, the connections are made in such a way that the first four (1, 2, 3, 4) cells in series Procedure form one unit, the next three (5, 6, 7) a second unit, the next When the apparatus is filled, the current is lurned on and two (8,9) a third unit, and the last cell (10) is alone. Each unit thus receives the benefit of the entire 110 volts, and, as allowed to run for from 20 to 30 mimtes. The siphons the purification proceeds and the removal of the salts in- (Figure 4) are then filled, and the feed water started at the creases the resistance, the cells of each succeeding nnit receive desired rate. When the amnieter (Figure 1, B) shows no a progressiveIy higher voltage. The average voltage of the further tendency to fa11 (usually aEter 30-40 minutes), the cells of the first unit is 27.5, of the next 36.G, and of the third 55, and the final cell, containing practically pure water, has the benefit of the full 110 volts to complete the removal of the Iast ions. The ions are prevented from accumulating in the electrode compartments by tho continuous washinz of the electrodes. The first eight cells are &shed with the solution feed wbter, and cells 9 and 10 are washed either wit11distilled water or electroosmose purified water. The solubion feed water, to be purified, flows from the tank into the center eompartment of the first cell through a hard-rubber funnel which carries the water to the bottom of the cell. From the first cell i t flows by means of a siphon into the bottom of the second and from that to the third and so through the entire ten cells. Salt solutions to be treated are prepared with distilled water. (See Figure 2.) The purified water runs by gravity directly into the purified-water storage, or it k allowed to run to waste. FiBure 2-General Layout of Water-Purifying Apparatw ~~
~
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
November, 1931
purified water is directed into the purified-water storage, and the apparatus left in operation for 1 hour before samples are taken for analysis. Sampling
1307
a t a constant rate. Adjustments were constantly necessary to keep all the electrodes supplied with wash water a t a uniform rate, especially when the solution was concentrated and the rate slow. SIZE OF CmLs-The hard-rubber dividers between the cells had a tendency to warp and cause a wide variation in the size of the compartments. Less wash water was left in contact with some electrodes, which might make a difference in the efficiency of the washing process.
Samples were taken from the raw feed water, from the third, sixth, and ninth cells, and from the purified water. The purified-water samples were taken first. The cells were then isolated by opening the cocks on the siphons, and the samples siphoned out through tube into - a glass 1-liter sample bottles. As soon as the samples i. were taken, the rate of flow was changed by exchanging the glass nozzles on the feed-water pipe, the siphons were filled, and the apparatus allowed to come to adjustment before another sample was taken. This procedure allowed the -taking of a set of samples about every Z1/4hours or the collection of six sets of samples between 7 A . B.I.and 9 P. 11. The analyses were run on the following days. The salts used as solutes were laboratory chemicals of c. P. grade. The water used as solvent was drawn from the distilled-water supply of the chemistry building, and the solutions mixed in a wooden mixing tank of about 1000 liters capacity. The solutions of the salts were made as uniform as possible and then were analyzed for the ions under investigation each time a set of samples was taken from the machine. D€TA/L OF E L F C T R O - O S M ~APPARATUS Methods of Analysis
The analysis carried out followed the procedure recommended by the American Public Health Association ( 1 ) . Chloride was titrated with standard silver nitrate solution, using potassium chromate as an indicator. Carbonate and bicarbonate were determined by titration with 0.02 N sulfuric acid, using phenolphthalein and methyl orange as indicators. Sulfate was determined gravimetrically by precipitation with barium chloride. Difficulties
DRIPNozzLEs-Difficulty mas encountered in keeping the drip nozzles, used in washing the electrodes, delivering water
Figure 4
IRON-There was a decided tendency, especially when solutions were concentrated, for red sediment to enter the machine from the iron feed-water reservoir. Precautions should be taken to prevent the formation of such sediment. The sediment was not readily removed by the electroosmose process but tended to settle in the bottom of the cells. Some was collected with the samples and thereby made the values obtained for residues inaccurate. The red color often showed in the residue on evaporation, especially in that from the intermediate cells. Dissolved iron seemed to vary also, although there was very little tendency for iron to appear in the final product. DESTRUCTION OF BaGs-At the high concentration of chloride, the chlorine formed in the anode compartments destroyed the canvas of the Z O Y W AC sypp/u L,c? cells. ;\lore r a p i d w a s h i n g when the salt concentration is high may be helpII ful. Experimental Data
Figure 3-Wiring
D i a g r a m for Control of Level in Feed Reservoir
Data were secured by the examination of over three hundred samples. These varied in composition, as they were taken from different cells of the electroosmose machine, with different concentration and rate of flow of the salt solutions treated. The samples belonged to five distinct groups: chloride, carbonate, chloride and carbonate, sulfate, and sulfate and carbonate. Each sample was examined for the negative ions present. CmoRIDE-so1utions of sodium chloride containing approximately 50, 100,150,200, and 500 p. p. m. of chloride ion were treated by the machine a t six different rates: 15, 20
INDUSTRIAL AND ENGINEERING CHEMISTRY
1308
25, 30, 35, and 40 liters per hour. During each run samples were taken from the feed water, from cells 3, 6, and 9, and from the final product. Each sample was analyzed for chloride and total residue. With an original concentration of 50 p. p. m. of chloride in the form of sodium chloride (Table I), the samples from the ninth cell showed a chloride concentration of less than 10 p. p. m. even a t the highest rates; a t 25 liters per hour (the rated capacity of the machine) the concentration was below 5 p. p. m. in the ninth cell and practically complete in the final product. An increase in concentration of the feed water to 100 p. p. m. made very little difference in the efficiency of removal, and even a t 150 and 200 p. p. m. the final product was practically free from chloride when the standard rate of the apparatus was not greatly exceeded. If the rate was increased to 35 liters per hour, the final product, even from the more concentrated feed waters, contained less than 10 p. p. m. of chloride, which is sufficiently pure for most purposes. There was more rapid removal of salts from the first eight cells with a much slower removal as the solution became more dilute and the removal of the last traces of salt mas attempted. I n the solution containing 500 p. p. m. of chloride (Table I), the limit of the machine appeared to be reached. While very good removal was noted in the final product, run a t 25 liters per hour, and while even in the ninth cell analysis showed only 8 p. p. m., two difficulties appeared which made it seem unwise to attempt the study of solutions of higher concentrations: When the apparatus was filled and the current was first turned on the conductivity was so high that additional resistance was necessary to protect the fuses, and 15 or 20 minutes were required before the salt was removed sufficiently to bring the conductivity below 30 amperes. Thirteen and one-half amperes were used when the solution flowed at the rate of 25 liters per hour, even after equilibrium had been reached, and much higher amperages were noted as the rate of flow was increased. The anode diaphragms of cells 2, 3, and 4 were so badly damaged that they had t o be replaced. This was probably due to the chlorine. No special study was made of this problem. T a b l e I-Sodium
SOURCE SAMPLE
15 c
Chloride Solution RATEIN LITERSPER HOUR 20 25 30 35 Amperes 2.5 2.75 3.00 3.50
40
-
2.5 4.00 P . p . m . P.p.rn. P . p . m . P . 9 . m . P . 9 . m . P . 9 . m . (APPROXIMATELY w P. P. M . CHLORIDE) 97.0 97.0 92.0 90.0 Feedwater Residue 88.0 89.0 63.0 53.0 53.0 52.0 C1 52.0 52.0 Cell3
Residue
c1
26.0 37.0
32.0 44.0
34.0 41.0
37.0 46.0
44.0 44.0
39.0 47.0
Cell6
Residue
8.0 11.0
12.0 17.0
6.0 23.0
9.0 25.0
17.0 31.0
13.0 33.0
Cell9
Residue
4.0 1.0
4.0 4.0
1.0 4.0
3.0 4.0
5.0 8.8
e:3
Purified Reddue product C1
5.5 0.0
5.5 1.0
5.0 1.0
3.0 1.7
4.0 1.0
2.0
Amperes 13.5 17.0 485.0 485.0 312.0 350.0 83.0 134.0 7.8 23.0
21.0 485.0 364.0 182.0 55.0
25.0 486.0 416.0 290.0 112.0
8.5
11.5
4.0
c1
c1
(APPROXIMATELTY LOO P. P. M. CHLORIDE) C
Feed water Cell 3 Cell 6 Cell 9 Purified product
C1 C1 C1 C1
9.0 484.0 200.0 23.0 1.8
11.0 485.0 242.0 53.0 6.4
CI
0.0
2.4
6.1
7
CARBONATE-Solutions containing approximately 100, 200, 250, and 300 p. p. m. of carbonate in the form of sodium carbonate were prepared, treated a t the same rates, sampled as mentioned before, and examined for carbonate, bicarbonate, and for total residue (Table 11).
Vol. 23, No. 11
T a b l e 11-Sodium C a r b o n a t e S o l u t i o n -RATE I N LITERSPER HOUR, 15 20 25 30 35 40 SOURCESAMPLE Amperes 1.5 1.75 1.75 2.0 2.0 2,50 P . 9 . m . P . p . m . P . 9 . m . P.9.m. P.9.m. P.9.m.
-
-
(APPROXIMATELY 100 P. P . M. CARBONATE)
COa Feed water HC03 Residue
90.0 17.0 172.0
94.0 21.0 175.0
88.0 21.0 173.0
88.0 25.0 173.0
94 12 175
79.0 40.0 175.0
COa HCO3 Residue
92.0 82.0
0
0 104.0 97.0
2.4 100.0 106.0
29.0 81.0 137.0
39 71 130
20.0 100.3 119.0
0
0 42 0 28 0
0
0
Lost 59.0
81 62
103 0 82.0
0 8 1 6 0
0 17 0 11 0
0 34 19
0 35 0 29.0
0 10 6
0 16.0 17.0
Cell3
cot
HCO3 Residue
17 0 17.0
0 24 0 22.0
cos HCO3 Residue
0 2.4 13 0
26 8 4 0
Purified COa product HCOI Residue
0 1 2 11.0
7.0
Cell 6
Cell 9
0
0
1.2
0 1.2 2.0
0
0
5.1 5.0
-
(APPROXIMATELY 300 P. P. M . C A R B O N A T E ) C
Amperes 5.0 5.5
4.5
4.5
5.6
5.9
Feed water HCOa Residue
cos
292.0 5.6 553.0
291.0 6.8 524.0
293.0 5.9 522.0
286.0 2.9 524.0
283 26 516
288 11 522
Cell3
COa HC03 Residue
236.0 53.0 461.0
224.0 68.0 457.0
212.0 82 0 452.0
250.0 45.0 480.0
254 61 483
255 43 492
Cell6
HCOa Residue
cos
86.0 172.0 310.0
39.0 233.0 280.0
112 0 163.0 345.0
162.0 125.0 403.0
184 414
166 121 409
Cell9
COa HC03 Residue
0 168.0 148.0
0
185.0 163.0
24.0 201.0 222.0
88.0 185.0 310.0
92 175 306
71 260 266
Purified product
COa “201 Residue
0 45 0 39.0
0 48 0 44.0
0 103.0 91.0
0 201 0 157.0
16 231 225
40 217 264
S5
The carbonate in the solutions treated showed a decided tendency to form bicarbonate a t all the rates studied. Lower rates appeared t o favor this change, allowing its completion a t an earlier period in the treatment. The final removal of the bicarbonate was retarded by increased rate of flow in all the solutions, and the removal was not nearly complete except a t rates below 30 liters per hour and a t concentrations below 250 p. p. m. of carbonate in the original solution. Twentyfive liters per hour is the rated capacity of the machine. MIXTURE OF CHLORIDE AND CARBONATE-Asolution was prepared containing about 250 p. p. m. of a mixture of chloride and carbonate in approximately equivalent amounts, Sodium chloride and sodium carbonate were used in this solution. The solution so prepared was treated by the machine a t rates of 15, 20, 25, 30, 35, and 40 liters per hour and samples taken as before. These samples were analyzed for chloride, carbonate, and bicarbonate (Table 111). A special run was made on a similar mixture a t 25 liters per hour in which each cell was sampled. These samples were analyzed for carbonate, bicarbonate, and chloride as before (Table 111). When chloride and carbonate in the same solution were run through the machine a t rates of from 15 to 40 liters per hour, a decided change was noted in the behavior of the carbonate radical compared to that observed in the previous solution containing carbonate alone. The carbonate was entirely removed by the time the third cell was reached in every case studied, and the bicarbonate which appeared a t 25 liters per hour (the rated capacity of the machine) in the third cell did not persist beyond the sixth cell. This was t o be expected since the tests on solutions of chloride alone showed a reaction acid to methyl orange in the third, sixth, and ninth cells. The presence of the acid favors the formation of HSC03, which decomposes to liberate carbon dioxide. The removal of the chloride seems to be in no way affected by the presence of the carbonate.
INDUSTRIAL, A.VD ENGINEERING CHEJIISTRY
November, 1931
In the treatment of a similar solution a t the rate of 25 liters per hour when a sample was taken from each cell, the actual point a t which the carbonate was completely removed was indicated as the second cell, while bicarbonate did not appear beyond the fourth cell. T a b l e 111-Sodium C a r b o n a t e a n d S o d i u m Chloride S o l u t i o n M i x t u r e (Approlimately 260 p. p. m. Equivalent cos, 120; CI, 142) RATEI N LITERSP E R HOTJR SOURCE SAMPLE 15 20 25 30 35 40 ,-Amperes-3.5 4.0 4.5 6.0 6 75 7.5 P.9.m. P.p.m. P.p.m. P . p . m . P.p.m. P.0.m. 118 0 118.0 116.0 121.0 118.0 COS 120.0 0 0 0 6.6 Feed Rater HCOa 0 2.7 142.3 141.0 140.0 143.0 142.0 CI 142.0 Cell 3
COa HCOa CI
Cell 6
HCOi
COT C1
Cell 9
0
0 55.0 0 0 9.0
COa HCOa Cl
COa Purified product HCOa
c1
SOURCE
0 0 1.0 0 0
0
0 45.0
45.0 0 0 20.0
0 5.1 74.0 0 0 10 0
0 0
0 0 2.0
0 0 8.0
0 0
0
0 0
0 0
0 0
0 36.0 0 0 14 0
0
0
0
7.3
86.0 0 0 35 0
8.4
0
86.0 83.0 0 0 39.0
0 0 12.0 0 0
1309
each while the sulfate hastened the removal of both carbonate and bicarbonate in much the same degree as was noted in the case of chloride. T a b l e V-Sodium Sulfate a n d Sodium Carbonate Solutiqn Mixture (200 p. p. m. sulfate; 200 p. p. m. carbonate) RATEIN LITERSPER HOUR 25 30 SOURCE SanPLE ' Amperes 6.00
7.00
P. p . m.
P. p . m.
Feed water
so4
198 172 50
196.0 173.0 44.0
Cell 3
so4
94 0 24
121,o 0.0 59.0
Coa HCOs Cos HCOa
Cell 6
36.4 0
Acid
Cell 9
so4
20 0 14
6.7 0.0 11.0
so4
5 0 12
3.8 0 12.0
Cos HCOa
Purified product
COa HCOa
0 0 1.5 2.0 2.50 3.0 Summary (Rate: 25 liters per hour) -CAMPLE---For the conditions of the experiment and the size of C1 Cos H(:Oa P. p. m. P. p . m. P.
