of Mineral Substances. 279 



came pale yellow and moderately turbid, the colour probably 

 resulting from a little oxalate of iron : the mixture became 

 slowly clear, and the precipitate being collected weighed after 

 ignition 2.5 grains, and had the properties of lime slightly con- 

 taminated by oxide of iron. 



The matter therefore, soluble in water, consists of sulphate of 

 lime and sulphate of iron, the relative proportions of which may 

 be estimated as follows : 1000 parts of the ore gave 46 of Iphate 

 of baryta = 15.18 dry sulphuric acid, of which 7 parts satu- 

 rated the 5 of lime, producing 15 parts of crystallized gypsum 

 The remaining 8.18 of acid combined with 8.5 of oxide of iron 

 would produce 18 parts of effloresced sulphate of iron. 



B. 



Two hundred grains of the ore were boiled in water with 400 

 of dry carbonate of soda ; the filtered liquid was of a dark brown 

 colour ; neutralized with muriatic acid, it afforded no trace of 

 sulphuretted hydrogen : this neutral solution gradually depo- 

 sited a bulky dark brown matter which, collected and dried, 

 weighed 12 grains, and which, heated in a platinum crucible, 

 burned away without any odour of sulphur, and left 1 grain of 

 white alumina. 



C. 



Two hundred grains were digested in muriatic acid, during 

 which not the smallest trace of sulphuretted hydrogen was per- 

 ceived, nor was there much action ; but during the gradual ad- 

 dition of nitric acid, nitrous gas was evolved and the black 

 colour of the ore became brown ; the filtered' solution was yellow 

 and mixed with muriate of baryta furnished 54 grains of sul- 

 phate of baryta (after ignition). 



D. 

 ^ a. 1000 grains of the ore recently from the mine, were heated 

 in a retort, the recipient being connected with the pneumatic ap- 

 paratus. 220 cubic inches of gas were evolved, having the pro- 

 perties of a mixture of sulphuretted and carburetted hydrogen. 

 b. The liquid produced weighed 133 grains; it was yellow 

 and smelt of hydro-sulphurct of ammonia ; it changed reddened 



