March, 1924
INDUSTRIAL A N D ENGINEERING CHEMISTRY
and grew a t a rapid rate. On the basis of these tests, it is evident that the oil from livers stored 6 months is fully as potent as that from fresh livers.
POTEKCY OF OILFROM LIVERSSTORED ONE YEAR The rcmlts of tests of the potency of cod-liver oil obtained from livers which had been in storage for slightly over a year are of particular interest. I n these tests (Chart 15) seven animals were fed oil in amounts graduated from 0.00022 to 0.00312gram daily. All these animals promptly responded to the addition of oil to their basal diet. When this series of tests was started, it was questioned whether as little as 0.003 gram of this type of an oil contained enough vitamin to keep a rat alive for the 45-day experimental period, and from past experience it seemed certain that those animals receiving less than 0.001 gram daily could not live long. Consequently, Rat 222 was included in the series as a check on Rat 204. The results of this series show that in one instance, a t least, as little as 0.00022 gram daily of the oil obtained from livers
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that had been stored for a year containedsufficient vitamin A to meet the requirements of albino rats for growth. It may be noted, however, that the oil rendered from the stored livers was decidedly less palatable than the oil obtained from the fresh livers. As regards appearance and palatability, the oil from the stored livers resembles oil obtained by the “rotting” process and is not in the least comparable to oil rendered from fresh livers. Comparing these results with those obtained from the study of oil rendered from fresh livers, it appears that cod-liver oil rendered from cod livers which have been stored a t a low temperature’and out of contact with the air has a higher vitamin A content than that rendered from fresh livers. The investigation of the effects of storage of livers on the vitamin A potency of oil obtained from them is being continued. The results of tests of the vitamin potency of oil rendered from livers which were stored in open containers and exposed to atmospheric changes mill be reported in a separate paper in the near future.
Simplification of t h e Separation of Zinc from Iron and Aluminium‘ By E. G. R. Ardagh and G. R. Bongard c N I V E R S r T Y OF T O R O X T O ,
TORONTO, CANAL4
HE: determination of At one time Kansas, Zinc can be separated completely from iron, and also from Missouri, Illinois, and Indizinc in ores always aluminium. by ammonium hydroxide and ammonium chloride .ana smelters could comnecessitates its sepain one precipitation. Two-tenths of a gram of each metal, or even mand a supply of ore averagration from iron. This is more, can be handled with celerity and ease. ing 0.5 to 1.5 per cent iron. usually accomplished (1) by Iron and aluminium hydroxides are precipitated in a compact While, it is true, conditions repeated precipitation of the state by evaporating their solutions to a oery small oolume, adding iron by ammonia, (2) by have changed, ample promore than suficient ammonium chloride to saturate the solution, vision has been made for ammoiiiuni carbonate, (3) and then adding concentrated ammonium hydroxide in considerablc much higher iron content by M basic acetate, or (4) by suction the erecieitate is casu to wash. excess. Bu using- gentle precipitation of zinc as zinc employing in the great sulfide in weakly acidified majority of experiments 0.2 solution. Not only are all these processes, as usually carried gram iron and 0.2 gram zinc, corresponding to 40 per cent of out, time-consuming, but in methods (3) and (4) the condi- each metal when 0.5 gram is taken for assay. Ingalls’z states tions m m t be maintained within quite narrow limits to insure that low-grade calamines assaying 40 per cent ferric oxide (28 per cent iron) have been smelted, but that with this exsuccess. It is the purpose of this article to show that perfect separ- ception no ores containing over 20 per cent iron are acceptable ations can be made quickly and conveniently with ammonia to zinc smelters. A .European smelter would rarely care, and ammonium salts, even when relatively large quantities says Ingalls, to have more than 10 per cent iron in his charge. I n New Jersey the ore smelted a t the present time contains 2 of the two metals are present at the same time. The determination of zinc in ores in North America is to 3 per cent iron, while the same authority says that in invariably carried out volumetrically by the ferrocyanide Kansas and Missouri probably few smelters carry more method. The method was first proposed by Galletti,2~* than 2.5 per cent iron in their charges. and the modification in use today is very well described in STANDARD SOLUTIONS A N I DETERMIKATIOK OF THE BLANK Low’s4 “Technical Methods of Ore Analysis.” Schaffner’s The standard ferrocyanide solution contained about method‘ never attained any vogue on this continent. Of all the authorities on the determination of zinc, A. H. 22 grams potassium ferrocyanide and 8 to 10 grams sodium Low is the only one who could be found who maintains that thiosulfate per liter.5 It was checked every 2 weeks against this metal can be completely separated from iron (when the pure ZnS04.7HzO solution containing 44.000 grams of the latter is present in more than very small amount) by ammonia pure salt per liter. One cubic centimeter of this solution and ammonium chloride by a single precipitation. All contained 0.0100 gram of zinc. The indicator used conother writers declare a double precipitation to be necessary. tained 15 gram UO(NO& in 100 cc. of water.lO To test the influence of varying the concentration of the Low states that zinc can be completely removed from precipitated ferric hydroxide by washing with a solution contain- ammonium chloride on the blank, a series of trials was made ing 100 grams ammonium chloride and 50 cc. concentrated in which the other factors were kept constant. ammonium hydroxide per liter, but he does not give any conNH&1 Added , KdFe(CN)s Required firmatory figures, nor state how much iron was present when TRIAL Grams cc. 1 5 0.16 lie carried out the experiments that led to his conclusion. 2 10 0.15
T
1 Received
3
July 2 5 , 1923.
* Numbers in text refer to bibliography a t
end of article.
4
5
20
30
40
0.15 0.15
0.16
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Vol. 16, No. 3
It is evident that the ammonium chloride can vary over a wide range, so that one can safely use large quantities of ammonium hydroxide and ammonium chloride if necessary in the separation of iron, neutralizing the ammonium hydroxide in the filtrate with hydrochloric acid. DETERMINATION OF K$e(CN)a REQUIRED ZIXC SOLUTION
FOR
Experiments on the separation of copper and nickel from iron carried out by the senior author13 proved astonishingly successful when the solutions were evaporated to 2 or 3 cc., thus making it possible to saturate them with ammonium chloride and make them very strongly ammoniacal without being compelled to employ extravagantly large quantities STANDARDof these two reagents. (2) Accordingly, 20 cc. standard zinc sulfate and 20 cc. ferric
sulfate were evaporated, with addition of two or three drops of' T o a 400-cc. beaker were added 20 cc. of the zinc sulfate concentrated hydrochloric acid to about 2 cc. Five grams solution containing 0.2000 gram zinc from a pipet, 5 cc. ammonium chloride and 10 cc. concentrated ammonium hyconcentrated hydrochloric acid (specific gravi(cy 1.19), 10 droxide (specific gravity 0.90) were added, the mass was thorgrams ammonium chloride, and water to 250 cc. The tem- oughly worked up with a stirring rod, and 40 cc. of cold water were added. The solution was filtered cold and washed four perature was maintained between 60" and 70" C. during times with cold water. The filtrate was titrated under the usual titration. The potassium ferrocyanide was added slowly, conditions. Zinc not faster than 10 cc. per minute, with constant stirring. K4Fe(CNh Zinc Zinc Retained by Zinc Too rapid addition may give a false end point, so that too Required Separated Present Fe(0H)a Present cc. Grams Per cent Per cent Per cent little potassium ferrocyanide is used. When the titration 37.35 0.1896 94.8 0.0104 6.2 is carried out as described the precipitate a t first produced Evidently, washing with water alone does not completely reis greenish or bluish white. After most of the potassium the zinc from the precipitate. The ferric hydroxide was ferrocyanide required has been added, the precipitate be- move quite dense, occupying only a fraction of the space required in comes quite flocculent and settles fairly quickly. About Experiment 1. Low'l has also observed this phenomenon, 0.5 cc. before this end point the solution turns a creamy and refers to it in his chapter on the determination of zinc. (3) Forty cubic centimeters of mixed sulfates and two drops of white, and the particles of the precipitate become much hydrochloric acid were evaporated to about 1 cc., smaller and will settle only after 2 or 3 hours' standing. The concentrated worked up with 5 grams ammonium chloride and 5 cc. conchange in size of the particles is more readily noticed if the centrated ammonium hydroxide, diluted with 25 cc. cold water, solution is allowed to stand for half a minute without stirring. filtered, and washed with 50 cc. of cold solution containing 5 The potassium ferrocyanide should now be added drop by grams ammonium chloride and 5 cc. concentrated ammonium drop, testing after each. By using a glass tube for stirring hydroxide per 100 cc. of solution. Zinc KdFe(CN)a Zinc Zinc Retained by Zinc three to four drops can be removed for each test. On arrivRequired Separated Present Fe(0H)a Present ing at the end point, one should wait 2 or 3 minutes to see cc. Grams Per cent Grams Per cent 39.25 0.1994 99.7 0,0006 0.3 if the immediately preceding one or two tests develop a color. From the reading decided on as being correct, the blank is In order to obtain a confirmatory check on the zinc retained by naturally to be deducted. the precipitate, the ferric hydroxide was dissolved in concenKdFe(CN)s Required cc. 1 39.50 2 39.70 39.55 3 4 39.55 '6 39.65 Average 39.60 Blank 0.15 Net KnFe(CN)a required 39.45 Therefore, 20 cc. ZnSOd solution require 39.45 cc. K,Fe(CN)e or 1 cc. KdFe(CN)s indicates 0.006070 g. Zn.
TRIAL
SEPARATION OF IRONFROM ZINC BY NH40H AND NH&l A solution of ferric sulfate containing very close to 0.01 gram iron per cubic centimeter was made up by stirring powdered Fez(SO&. 9Hz0 into warm water faintly acidified with sulfuric acid. The following series of experiments was performed with 20 cc. of this solution and 20 cc. of the standard zinc sulfate-i. e., 0.2 gram of each metal. Precipitation was carried out in a volume of about 150 to 200 cc., the solution being heated to boiling. The solution was filtered hot, using suction, and washed as described in each case. The filtrate was neutralized with concentrated hydrochloric acid and 5 cc. in excess added. Five grams ammonium chloride were then added, the solution made up to 250 cc. and titrated a t 60" to 70" C. as before. (1) Twenty-five cubic centimeters 5 N ammonium hydroxide and 5 grams ammonium chloride were added: K&Fe(CN)s Zinc Required Separated TRIAL Cc. Grams 1 35.40 0.1794 2 30.10 0.1830
Zinc Present Per cent 89.7 91.5
Zinc Retained by Fe(0H)a Grams 0,0206 0.0170
Zinc Present Per cent 10.3 8.5
The precipitate, which was washed three times with hot water, was very bulky, filling a S-cm. paper about three-quarters full. These two trials make it clear that even when very considerable quantities of ammonium chloride and free ammonium hydroxide are present, a single precipitation does not by any means remove all the zinc from the ferric hydroxide.
trated hydrochloric acid, precipitated with concentrated ammonium hydroxide, filtered, and washed with ammonium chloride-hydroxide solution. KIFe(CN)e required 0.10 cc. Zinc present, 0.25 p& cent (0.0005gram)
The precipitate produced on addition of the potassium ferrocyanide was just discernible. (4) .This was carried out exactly as in (3), except that the precipitate was washed with 100 cc. of cold solution containing 5 grams ammonium chloride and 5 cc. concentrated ammonium ydroxide.
39.35 39.40 39.35 39.46 39.'&0 39.50 39.35
0.1996 0.1998 0.1996 0,2000 0.1998 0.2002 0.1996
99.8 99.9 99.8 100.0 99.9 100.1 99.8
0.10 0.05 0.05 0.00 0.05
0.0005 0.0002 0.0002 0.0000 0.0002
0.25 0.1 0.1 0.0 0.1
0.00 0.00
0.0000
0.0
