I N D U S T R I A L A N D ENGINEERING CHEMISTRY
March, 1924
(5) These separations were carried out exactly as those recorded under (4), except that the precipitate was filtered hot and washed with hot ammonium chloride-hydroxide solution of the concentration already given. TRIAL I 2
KaFe(CN) o Required cc. 39.40 39.30
Zinc Present Per cent 99.9 99.8
Zinc Separated Grams 0.1998 0.1996
When tested for zinc with potassium ferrocyanide, the washed ferric hydroxide gave a faint white precipitate in each case after standing 15 minutes. This indicates only a small fraction of a milligram of zinc. Evidently the method works satisfactorily both hot and cold. ( 6 ) The following separations were carried out exactly as those recorded under (4), using in each trial 100 cc. of wash solution containing 5 grams ammonium chloride and 5 cc. concentrated ammonium hydroxide. TRIAL 1
2 3 4
Zinc Taken Grams 0.2000 0.4000 0.2000 0.2000
Iron Taken Grams 0.3 0 2 0.1. 0.4
K4Fe(CN)s Zinc Required Separated Cc. Grams 39.55 0.2002 78.96 0.4000 39.50 0.2000 39.35 0.1996
Zinc Taken Per cent 100.1 100.0 100.0
99.8
In Trial 1 the wash solution was hot; in Trials 2, 3, and 4 it was cold. The washed ferric hydroxide in Trial 2 contained enough zinc to give a faint precipitate of zinc ferrocyanide on 2 hours’ standing. The precipitate was much smaller than one produced by 0.5 mg. of zinc. Zinc could not be detected in the washed ferric hydroxide from Trial 3, but in Trial 4 a faint test was obtained. It is evident that 0.2 gram of zinc can be completely separated from as much as 0.4 gram of iron in one precipitation by the foregoing simple procedure. When such a large quantity as 0.4 gram iron was present, the most satisfactory technic was found to be the following: To the zinc-iron solution in a beaker or casserole add a few drops of concentrated hydrochloric acid and evaporate to about 5 cc., taking care to avoid local baking. Then take the vessel in the hand and swirl the contents while continuing the evaporation over a small flame, until the volume is reduced to about 2 or 3 cc. While still warm add 5 grams ammonium chloride and work up the mass with a stirring rod. Add 10 cc. concentrated ammonium hydroxide, break up lumps, add about 25 cc. cold water, and filter on a 7-cm. paper in an 8-cm. Biichner funnel. Wash back the bulk of the precipitate into the beaker or casserole, using the ammoniacal wash (5 grams NH&l 5 cc. concentrated “40H made up to 100 cc.) and transfer again to the filter. Wash six to eight times on the filter, consuming about 100 cc. of the ammoniacal wash liquid in all. Neutralize the ammoniacal solution with concentrated hydrochloric acid, adding about 5 cc. in excess, dilute to about 250 cc., and titrate at from 60” to 70’ C. in the manner already described. A powerful suction packs the precipitate on the paper too tightly, and hence should be avoided. A suction equivalent to about 76 mm. of mercury works very satisfactorily, and with i t the whole operation of filtering and washing should not require more than about 5 minutes. When handling smaller quantities of iron, say 0.1 to 0.2 gram, an ordinary funnel is quite satisfactory, but with larger quantities the precipitate packs in the apex of the paper.
+
SEPARATION OF ZIXC FROM ALUMINIUM Upon separating zinc from aluminium, a small amount of aluminium passes into the filtrate owing to the slight solubility of aluminium hydroxide in solutions strongly alkaline with ammonia, but not enough dissolves to interfere with the subsequent titration of zinc. A test determination gave 4 mg. aluminium in the filtrate. A solution containing very nearly 0.01 gram aluminium per cubic centimeter was made from A12(S04)a. 18Hz0, a few drops of sulfuric acid being first added to the water. (7) Twenty cubic centimeters of standard zinc sulfate and 20 cc. of the aluminium sulfate were treated exactly as in Experiment 4. KiFe(CN)s far &nc- Re;-Zinc tained by Zinc Present Al(0H)a Retained Per cent Cc. Grams 99.5 0.15 0.0008 99.9 0.00 0.0000 99.9 Reauired -.
ICaFe(CN)s Zinc Required Separated Grams 39.25 0.1990 39.40 0.1998 39.40 0.1998
TRIAL Cc. 1
2 3
Zinc Present Per cent 0.4 0.0
299
The washed aluminium hydroxide was tested for zinc exactly as described in Experiment 3. The aluminium hydroxide formed in the concentrated ammonium hydroxide saturated with ammonium chloride, like the ferric hydroxide formed under the same conditions, is much denser than that produced in the usual way. In Trial 2 zinc could not be detected in the washed aluminium hydroxide. In Trial 3 a faint precipitate of zinc ferrocyanide appeared.
Zinc can evidently be separated from aluminium without difficulty in one precipitation, when as much as 0.2 gram of each metal is present, by ammonium hydroxide and ammonium chloride. The precipitate of aluminium hydroxide appears to require somewhat more washing than the ferric hydroxide. (8) To compare Demorest’s methodg with that of the writers, they proceeded exactly as in Experiment 4,except that they used 5 grams powdered ammonium carbonate in place of 5 cc. concentrated ammonium hydroxide. The wash solution also contained 5 grams ammonium carbonate per 100 cc. in place of 5 cc. concentrated ammonium hydroxide. Using 20 cc. of standard zinc sulfate and 20 cc. aluminium sulfate. KaFe(CN)o Required cc. 38.45
Zinc Separated Grams 0.1950
Zinc Present Per cent 97.5
Care was taken to prevent loss through effervescence when adding hydrochloric acid to the filtrate. It is evident that ammonium carbonate, though effective, does not give quite so satisfactory a separation as concentrated ammonium hydroxide.
BIBLIOGRAPHY I-Schaffner, J . puakt. Chem., 73, 205, 410 (1852). a-Galletti, Bull. sot. clzim., I21 2, 83 (1864). 3-Fahlberg, 2. anal. Chem., 18, 379 (1874). 4-de Koninck and Prost, Z. angew. Chem , 9, 460, 564 (1896). 5-Waring, J . A m . Chem. Soc., 26, 4 (1904). 6-Stone and Waring, I b i d . , 29, 262 (1907). 7--Seaman, Ibid., 29, 205 (1907). &Lenher and Meloche, 8th Intern. Cong. A p p l . Chem., 1, 279 (1912). 9-Demorest, J . Znd. Eng. Chem., 6, 302 (1913). 10--Nissenson, “Die Untersuchungsmethoden des Zinks ” 11-Low, “Technical Methods of Ore Analysis.” 12--Ingalls, “Metallurgy of Zinc and Cadmium,” 2nd ed., p. 500. 13-Arrlagh and Broughall, Can. Chem. Met., 7, I98 (1923).
Gas H a z a r d s Warning as to the deadly hazards of gas in unventilated rooms and garages is again sounded by the Bureau of Mines. Seldom a day passes a t this season of the year but the press records the death of one or more persons by asphyxiation in their homes or garages. It should never be forgotten that in burning natural gas carbon monoxide may be given while in the exhaust from an engine this gas is practically always present in exceedingly dangerous amounts. Many house heaters have no flues for carrying off the waste gases, which then pass into the rooms. If all windows and doors are closed, the effect of these gases sooner or later becomes apparent on the occupants, who become dull and sleepy, and sometimes die. If a gas heater without a flue is used, a window should be partly open all the time-that is, up a half inch or so. Even heaters with flues should be in well-ventilated rooms. Never go to bed with a heater burning and the windows and doors closed. If the engine of an automobile must be kept running while making repairs, the garage must be ventilated. Never crawl under a car when the engine is running, no matter how good the ventilation. If it is desired to sit in an automobile with the engine running, the garage must have proper ventilation. Another hazard of exhaust gas is that of sitting in a tightly closed automobile, on a highway or elsewhere in the open, with the engine running. The car may be fitted with a leaky heater, through which the exhaust gas gets into and concentrates in the car, or else the exhaust from the muffler in some manner gets into and accumulates in the car. Publications bearing upon this subject may be obtained free from the Bureau of Mines, Washington, D. C.
