OF ARTS AND SCIENCES : MARCH 14, 1865. 473 



Having recently had occasion to determine sulphur in some volatile 

 liquid compounds, for which neither of the processes now in use seemed 

 satisfactorily adapted, I was naturally led to make an effort to utilize 

 my safety-tube and the stream of oxygen in this species of analysis also. 

 But the fact that sulphur is usually, at least, but partially converted into 

 sulphuric acid by combustion in oxygen gas, seemed at first to present 

 a difficulty not to be easily overcome. It soon occurred to me, however, 

 that the well-known reaction between sulphurous acid and peroxide of 

 lead, by which the former is completely converted into sulphuric acid, 

 might probably serve to remove this objection. Furthermore, that by 

 placing the peroxide of lead within the combustion-tube in the manner 

 which I shall presently describe, and by maintaining the peroxide of 

 lead at a temperature sufficient to prevent condensation of water within 

 the combustion-tube, the carbon, hydrogen, and sulphur might all be 

 determined from the same portion of substance. This result has been 

 accomplished.* 



Referring to my former paper above mentioned for details regarding 

 the construction and use of the apparatus employed, I need here de- 

 scribe only such modifications as have been found expedient to adapt 

 the process to this special purpose. 



The combustion-tube being packed with pure asbestos between the 

 points a and S, Fig. I., Fig. i. 



and the space — about 

 two inches in length — 

 between b and c left va- 

 cant, a plug of pure as- 

 bestus is placed at c, and 



* Carius (Annalen der Chemie und Pliarmacie, 1860, CXVI. 28) has observed 

 that when substances rich m sulphur are burnt with oxide of copper — a tube con- 

 taining peroxide of lead being placed between the chloride of calcium tube and the 

 potash bulbs in the usual manner — the determination of carbon is too liigh. And 

 on the other hand he found that, with substances rich in carbon the determination 

 of the carbon was too low. In the latter case the peroxide of lead was supposed 

 to absorb and retain carbonic acid ; and in the former, sulphurous acid was found 

 to pass unabsorbed through the peroxide of lead. 



The incomplete absorption of the sulphurous acid may be reasonably accounted 

 for on the supposition that a channel was formed, by handling or jarring, along the 

 top of the peroxide of lead, which indeed would be very likely to occur in using, by 

 itself, so heavy a powder. Through such a channel sulphurous acid might pass, 

 in so small proportion, without coming in contact with the peroxide of lead. It 



