46 PYROMETALLUKGY. [ill. 



very small quantities of copper and arsenic are contained in 

 all iron-ores, in ochres, ochreous deposits from springs, marls, 

 and meteoric masses. It may be proved by dissolving them 

 in pure muriatic acid, passing sulphuretted hydrogen through 

 the solution to saturation, and suffering the precipitate to settle 

 in a stoppered bottle. See also Buchner, Jr., on the content 

 of arsenic, copper, and tin in the mineral waters of Bavaria. 

 (Gelehrte Anzeigen d. K. B. Acad. d. Wissenschaften, No. 

 75,1847 ; Schaf hautl Untersuch. d. Eisenerze, Dingler's Journ. 

 Ixxiv. 303.) 



Pelouzes Alhalimetrie Test. — This method, both exact and 

 rapid, depends upon the perfect precipitation of copper from 

 its ammoniacal solution by sulphuret of sodium, and the exact 

 point is indicated by the change from a deep-blue to a color- 

 less solution. 



One gramme of the substance to be tested is dissolved in 

 7-8 cubic centimetres of nitric acid, the solution diluted with 

 water, and, after precipitating any silver that may be present 

 with muriatic acid, treated with 20-25 cubic centimetres of 

 caustic ammonia. A precipitate of lead or tin may be filtered 

 off. 110 grms. of crystallized sulphuret of sodium are then 

 dissolved in 1 litre water, and poured into a graduated alkali- 

 metric tube. To a boiling solution of 1 grm. pure copper in 

 nitric acid, treated with excess of ammonia, this test-liquor is 

 added, carefully noting the number of measures required to 

 decolorize the solution ; suppose, 31 measures. Treat the 

 solution of the substance to be tested, in a similar manner, 

 and suppose it requires 30 measures to decolorize it. It con- 

 tains, in this case, |f copper, of the quantity employed. 

 That is, multiply the quantity of the substance to be tested 

 (say 10, 20, or 100 grains) by the number of measures em- 

 ployed with pure copper, and divide by those employed for the 

 other solution. Then, if 20 grs. had been used, multiply the 

 quotient by 5, to bring the result to a percentage, &c. The 

 test should always be performed with a boiling solution. The 

 precipitate is 5CuS2+CuO. (See the Technologiste, Avril, 

 1846.) 



