1 24 Dr. Ure on Gunpowders 



quicken the precipitation of that portion which the boiling 

 motion may have kept afloat. When no more is found to fall, 

 one kilogramme of Flanders glue, dissolved in a sufficient 

 quantity of hot water, is poured into the boiler ; the mixture 

 is thoroughly worked together, the froth being skimmed off, 

 with several successive inspersions of cold water, till 400 ad- 

 ditional kilogrammes have been introduced, constituting alto- 

 gether 1000 kilogrammes. 



When the refining liquor affords no more froth, and is 

 grown perfectly clear, all manipulation must cease. The fire 

 is withdrawn, with the exception of a mere kindling, so as 

 to maintain the temperature till the next morning at about 

 88 C. = 190.4 Fahrenheit. 



This liquid is now transferred by hand-basins into the 

 crystallizing reservoirs, taking care to disturb the solution as 

 little as possible, and to leave untouched the impure matter at 

 the bottom. The contents of the long crystallizing cisterns 

 are stirred backwards and forwards with wooden paddles, in 

 order to quicken the cooling, and the consequent precipitation 

 of the nitre in minute crystals, which is raked, as soon as it 

 falls, to the upper ends of the doubly inclined bottom of the 

 crystallizer. It is thence removed to the washing chests or boxes. 

 By the incessant agitation of the liquor, no large crystals of 

 nitre can possibly form. When the temperature has fallen to 

 within 7 or 8 Fahrenheit of the apartment, that is, after seven 

 or eight hours, all the saltpetre that it can yield will have been, 

 obtained. By means of the double slope given to the crystal- 

 lizer, the supernatant liquid is collected in the middle of the 

 breadth, and may be easily laded out. 



The saltpetre is shovelled out of the crystallizer into the 

 washing chests, and heaped up in them so as to stand about 

 six or seven inches above their upper edges, in order to com- 

 pensate for the subsidence which it must experience in the 

 washing process. Each of these chests being thus filled, and 

 their bottom holes being closed with plugs, the salt is be- 

 sprinkled from the rose of a watering-can with successive 

 quantities of water saturated with saltpetre, and also with pure 

 water, till the liquor, when allowed to run off, indicates by the 

 Hydrometer a saturated solution. The water of each sprinkling 



