128 Dr. Ure on Gunpowders 



a rare vapour, and be deposited in a pulverulent form called 

 flowers ; for the only object of the refiner is to bring over the 

 whole of the pure sulphur into his condensing chamber, and 

 to leave all its crudities in the body of the still. Hence a strong 

 fire is applied to elevate a denser mass of vapours, of a yellowish 

 colour, which passing over into the condenser, are deposited in 

 a liquid state on its bottom, whilst only a few lighter particles 

 attach themselves to the upper and lateral surfaces. The refiner 

 must therefore give to the heat in this operation very consider- 

 able intensity ; and at some height above the edge of the boiler, 

 he should provide an inclined plane, which may let the first ebul- 

 lition of the sulphur overflow into a safety recipient. The 

 condensing chamber should be hot enough to maintain the dis- 

 tilled sulphur in a fluid state, an object most readily procured 

 by leading the pipes of several distilling pots into it ; while the 

 continuity of the operations is secured, by charging each of the 

 stills alternately, or in succession. The heat of the recipient 

 must be never so high as to bring the sulphur to a syrupy con- 

 sistence, whereby its colour is darkened. 



In the sublimation of sulphur, a pot containing about .four 

 cwt. can be worked off only once in twenty -four hours, from the 

 requisite moderation of its temperature, and the precaution of 

 an inclined plane, which restores to it the accidental ebullitions. 

 But by distillation, a pot containing fully ten cwt. may com- 

 plete one process in nine hours at most, with a very considerable 

 saving of fuel. In the former plan of procedure, an interval 

 must elapse between the successive charges ; but in the latter, 

 the operation must be continuous to prevent the apparatus from 

 being cooled : in sublimation, moreover, where communication 

 of atmospheric air to the condensing chamber is indispensable, 

 explosive combustions of the sulphurous vapours frequently 

 occur, with a copious production of sulphurous acid, and cor- 

 respondent waste of the sulphur ; disadvantages from which 

 the distillatory process is in a great measure exempt. 



I shall here give an outline of the form and dimensions of 

 the distilling apparatus employed at Marseilles in purifying 

 sulphur for the national gunpowder-works, which was found 

 adequate to supply the wants of Napoleon's great empire. This 

 apparatus consists of only two still-pots of cast iron, formed 



