I N D U S T R I A L A N D ENGINEERING CHEMISTRY
September, 1924
963
Aluminium in Alloys’ By Dorothy H. Brophy GENERAL ELECTRIC Co.,SCHENECTADY, N. Y .
T
HE increasing use of aluminium in alloys called for the development of a simple and rapid method for the analysis of this metal. The phenylhydrazine and phosphate methods were found too long and too difficult to be handled by inexperienced workers. Moreover, these methods could be used only in certain separations. Where it was necessary to remove aluminium from nickel, the basic acetate method had to be used, separating the iron and aluminium together, followed by a volumetric determination of the iron. Copper, iron, nickel, manganese, chromium, zinc cobalt, tin, bismuth silver, lead, and cadmium2 may be deposited electrically on a mercury cathode in dilute sulfuric acid solution. Aluminium and titanium will be found in the electrolyte. I n the development of this method, we were interested only in the separation of aluminium from copper, iron, nickel, manganese, and chromium.
TABLE I1 Alloy 1114 24
METHOD
9
Only sulfate solutions can be used. The synthetic solution of iron, nickel, and aluminium containing five drops of concentrated sulfuric acid in a volume of 100 cc. was transferred to a 150-cc. electrolysis beaker with about 0.63 cm. of mercury a t the bottom. A current density of 1 ampere 6.25 sq. cm. was found to be the most satisfactory for the rapid removal of the metals without heating the solution too much. A constant stirring a t the rate of 600 r. p. m. was maintained. I n 45 minutes no trace of iron or nickel was found in the electrolyte. The clear liquid was siphoned off, using a suction flask and washing the mercury with 150 cc. of distilled water while the current was still on. The aluminium was then precipitated as aluminium hydroxide in a volume of 100 cc. Methyl red was used as an indicator. The neutralization with the ammonia must be done very carefully, since aluminium hydroxide is soluble in ammonium h y d r ~ x i d e . ~The precipitate was filtered while hot, washed several times with hot water, dried, and ignited in a weighed platinum crucible to A1203. Samples were analyzed, using the procedure just described. About 1.5 hours were required for a complete analysis. Fourteen-hundredths gram of iron and 0.14 gram of nickel were added to each sample. TABLE I --ALUMINIUM-Taken Found Grams Grams 0.1095 0.1095 0.1107 0.1111 1,0583 0.05s1 0.0620 0.0604 0.0804 0,0804 0.0735 0.0736 0.0719 0.0719 0.0962 0.0966 0.0299 0.0300 0.0213 0.0213 0,0220 0.0215
10 cc. of water, and a few drops of nitric acid. Then 5 cc. of concentrated sulfuric acid were added and the solution was evaporated to fumes of sulfur trioxide. When cool, 20 cc. of water were added, the solutions were heated to dissolve and neutralized with ammonia. The solution was diluted to 100 cc. with water, then treated with five drops of concentrated sulfuric acid and electrolyzed for 45 minutes. The colorless electrolyte was siphoned off and the aluminium precipitated as previously described. The amount of aluminium in these alloys varied from 1.00 to 12.00 per cent, and in every case the oxide was pure white and no trace of iron, chromium, or nickel could be found. Some of the results are indicated in Table 11.
30 1
--ALUMINIUM-Grams Percent 0.0111 0.93 0.0092 0.89 0.0264 9.50 0.0195 9.53 0.0231
0.0234 0.0321 0.0328 0.0348 0.0282
11.13 11.21 10.98
11.11 5.42 5.30
If the alloys contain silicon, SiOz separates upon sulfuric acid dehydration and must be filtered before the electrolysis is made. Titanium, if present, remains with aluminium and must be determined colorimetrically in the ignited oxides. The mercury used for the cathode may be replaced after each electrolysis or may be used until it has absorbed approximately 0.6 gram of iron and 0.6 gram of nickel. When used too long, it becomes stiff and blistered on the surface and will not absorb any more metal. The procedure for the separation of aluminium in alloys containing copper, iron, manganese, nickel, and aluminium differs only in the solution of the sample. About 0.3-gram samples were dissolved in 10 cc. of (1: 1) nitric acid and 0.5 cc. of hydrochloric acid, then evaporated with 5 cc. of concentrated sulfuric acid. I n electrolysis copper separates a t once on the mercury, but with alloys containing 65 per cent nickel in 0.25 to 0.3-gram samples it may take 1.5 hours to remove the last traces of nickel. I n every case the A1203is obtained pure white, free from the other metals. Some of the results are indicated in Table 111. TABLG I11
Error Mg.
0.0
+0.4
Alloy 1
-0.2 +0.2
2
0.0 +o. 1 0.0 +0.4 -0.1 0.0 -0.5
3
--ALUMINIUM-Grams Percent 0.0085 0.81 0,0026 0.85
0.0059
1 05
0.0077
1.91 2.84 2.88 2.80 2.81 3.52 3.51 2.93 3.02
19 16
23
ANALYSIS OF ALLOYS Twenty-five hundredths to 0.3 gram samples of the alloys containing iron, nickel, chromium, manganese, and aluminium were dissolved in 5 cc. of concentrated hydrochloric acid, 1
Received M a y 10, 1924.
* Smith, “Electro-Analysis,” 3
P . Blakiston’s Son & Co.,1907.
Blum, J . A m . Chem. SOC..38, 1282 (1916).
Chemical Society Formed in I n d i a The Indian Chemical Society has been formed with headquarters a t Calcutta. Sir P. C. Ray is the president; J. I,. Simonsen and G. J. Fowler, vice presidents; P. C. Nutter, treasurer; E. R. Watson, editor. The first issue of the Journal os the Indian Chemical Society was scheduled to appear in August.
