Miscellanies. 387 



and boiled in another flask, the contents of the receiver were added 

 to the sulphur and a portion of the acid distilled from it, till its solu- 

 tion and entire conversion into sulphuric acid v^^as insured. There 

 remains a white insoluble powder, which, after ignition, weighed 10.1 

 and was composed of silica and alumina, derived from the mortar. 



III. The fluid and washings from the powder in II. were evapora- 

 ted, with a slight excess of ipuriate of baryta ; when much reduced, 

 water was added, and the precipitated sulphate collected on a double 

 prepared filter, was washed in muriatic acid, and then with water, 

 until all traces of foreign matter were removed ; dried and calcined 

 with the upper filter, there were 1294.1 parts, containing .8 ashes, 

 leaving 1293.3 sulphate of baryta, equal to 178.4 of sulphur. It 

 was white, and contained no arsenic. 



IV. When the washings were mixed with the fluid from the sul- 

 phate of baryta of III. an acid, pale yellow liquid resulted ; this 

 was divided into two equal parts by weight, one being used for the 

 analysis, the other as a check on the results by different processes. 

 The quantity of fluid equal to 500 parts of the mineral, being, in 

 the usual way, decomposed by an excess of hydrosulphuric acid 

 gas, the yellow sulphuret of arsenic, when dry, weighed 488.8 ; by 

 nitric acid and muriate of baryta, it was decomposed into 281.6 

 sulphur and 207.2 arsenic, or 414.4 for 1000 parts. 



V. After separating the sulphuret of arsenic, the liquor of IV. was 

 of a pale pink color ; it was evaporated at 120° in dry air ; when 

 much reduced, nitric acid was boiled with it to render the oxides 

 peroxides; while warm, it was rendered brown and neutral, by pure 

 ammonia, the last drop slightly impairing its transparency; the ox- 

 ides vi^ere then precipitated by pure ammonia, and lastly by hydro- 

 sulphate of ammonia, collected as before, dried and ignited. It was 

 found, from repeated trials, that the weight of the mixture suffered 

 no alteration by exposure to heat, for a longer or shorter time ; its 

 true weight was 278.6. It was a soft, cinnamon brown powder. 



VI. The dry oxides were dissolved in muriatic acid ; by adding 

 ammonia, the solution was neutralized, and succinate of ammonia 

 separated the iron, without precipitating a trace of cobalt ; after cal- 

 cination, it weighed 237.6, equivalent to 164.7 of iron, or 329.4 in 

 1000 parts. The difference between 237.6 and 278.6 is 41. which 

 is the weight of the protoxide of cobalt, representing 32.25 cobalt, 

 or 64.5 in 1000 : it was free from nickel. 



