Prof. Chapman on the Assaying of Coals by the Blowpipe. 443 



of the sulphur is a much more troublesome operation. A pro- 

 cess given by Earthier, in his Traite des Essais par la voie seche, 

 consists in boiling the ferruginous ash in hydrochloric acid, which 

 dissolves out the sesquioxide of iron, and then calculating the 

 sulphur from the loss. One hundred parts, for example, of sesqui- 

 oxide of iron correspond to 70'03 of metalhc iron ; and hence to 

 150-24 of iron pyrites, or to 80-21 of sulphur. But this method, 

 besides requiring a larger quantity of ash than can be conveniently 

 prepared in these blowpipe examinations, exacts that the other 

 portion of the ash be not attackable by the acid, — a condition 

 which of course does not obtain in the case of calcareous ashes. 

 For this reason, the process recommended by Rose and other 

 chemists is preferable, although somewhat beyond the i-ange of 

 blowpipe examinations. About 200 milligrammes of the coal 

 in fine powder are to be intimately mixed with 8 parts of nitrate 

 of potash, 4 of carbonate of potash, and 16 of common salt, and 

 the mixture fused in a platinum crucible over the spirit-lamp, 

 with the wick \vell pulled up, oi', better still, over a double-cur- 

 rent or Berzelius's lamp. The fused mass is then to be dis- 

 solved out in boiling water to which a few drops of hydrochloric 

 acid have been added, and the sulphuric acid thrown down by 

 chloride of barium. By dividing the precipitate thus obtained 

 (after filtration, careful washing, and ignition) by 7-25, we get 

 the amount of sidphur. 



As the above process, although simple enough in the perform- 

 ance, is scarcely available when the operator is away from home, I 

 have attempted to hit upon a more ready method, and one more 

 properly within the legitimate pale of blowpipe experimentation, 

 of ascertaining approximatively the amount of sulphur in coal 

 samples. After various trials, I have fouiid the following process 

 sufficiently exact for all ordinary cases, because, as a general rule, 

 we merely require to know here, if the coal under examination 

 be slightly, moderately, or highly sulphurous. It consists essen- 

 tially in comparing the intensity of the stain produced on silver 

 foil by an alkaline sulphide of known composition with that 

 formed by an alkaline sulphide obtained from the assay-coal. 

 For this purpose, mixtures must first be made of a coal free from 

 sulphur, with such proportions of iron pyrites as correspond re- 

 spectively to a i)er-centage of 2, 4, G, ,8, and 10 |)arts of sulphur. 

 These proportions are the following: — Coal, 9626; pyrites, 3-74 

 = sulphur 2 per cent. Coal, 92-50; pyrites, 7-50 = sulphur 4 

 per cent. Coal, 88-76; pyrites, ir24 = sulphur 6 per cent. 

 Coal, 85; pyrites, 15 = suli)hur 8 per cent. Coal, 81-27; 

 pyrites, 18-73 = sulphur 10 per cent. Separate portions of each 

 of these mixtures are to be fused in a platinum spoon with three 

 j)arts of a mixture of five jjarts of carbonate of soda with one 

 2 G2 



