764 GUNPOWDER 



vessel. The latter is a large shallow pan with sloping sides. The fluid is constantly 

 stirred as it cools, in order that the crystals formed may bo very small ; this is done 

 in order to facilitate the washing process, and also because the fine powdery crystals 

 are well adapted for admixture with the other ingredients. When the crystallising 

 solution is cold, the nitre is removed to boxes containing false bottoms, pierced with 

 holes. The aperture in the bottom of the box (below the false bottom) being closed, 

 a saturated solution of pure nitre is poured on the crystals to dissolve out the chloride 

 of sodium. Being already saturated, it is evident it cannot dissolve any of the nitre. 

 After remaining two hours in contact with the nitre, the solution is allowed to run off, 

 and when the dropping has almost entirely ceased, the process of washing is rrj 

 substituting pure water for the solution of nitre. The product is dried at a gontlo 

 heat, being constantly stirred to enable it to retain the pulverulent form. The power 

 (above alluded to) possessed by a saturated solution of nitre, of dissolving other salts, 

 has been taken advantage of in one of the processes for analysing saltpetre. Some 

 manufacturers fuse the nitre after it has been purified by crystallisation ; this process 

 lias several disadvantages, among others that of necessitating machinery to reduce it 

 again to a pulverulent state. 



Preparation of the Sulphur. Sulphur may be purified for the gunpowder-maker by 

 two processes. In the first the crude article is fused in an iron pot, so contrived that 

 the fire does not play directly on the bottom, but only round its sides. The lighter 

 impurities are to be removed by skimming, while the heavier sink to the bottom. 

 The temperature should not be allowed to rise much above 232, for it then bo- 

 comes sluggish, and at 320 it is so thick as to prevent the impurities from being 

 removed. 



Sulphur may be more readily and economically purified by distillation. The appa- 

 ratus for the purpose is exceedingly simple in principle ; but the process requires care, 

 and is not entirely free from danger. As it is not intended to obtain the sulphur in 

 the state of flowers, the apparatus for condensation is not required to be kept cold ; 

 in fact, the still is purposely placed so near to the chamber of condensation that the 

 sulphur may be received in the fluid state. There are several points which must be 

 attended to in the construction of an apparatus for the distillation of sulphur ; they 

 are as follow: 1. The crude sulphur must be capable of being introduced, and the 

 refined product removed easily, without air being, at the same time, permitted to 

 enter the still or condenser. 2. Free means of egress for the heated air must be 

 provided. 3. The contrivance for the latter purpose must not allow fresh air to return. 

 4. The process must be continuous. The still and condenser employed in France for 

 the purification of crude sulphur fulfils all these conditions. The still is in the form 

 of a very wide-necked tubulated retort, made of cast iron. It is set in brickwork over 

 a furnace, and opens into a square brick chamber surmounted by a dome. The latter 

 has a rather short chimney over it, containing a valve opening upwards to permit 

 escape of the heated air, but not allowing anything to return. Over what may be 

 termed the tubulature of the retort or still, is placed an iron pot with a tube commu- 

 nicating with it. The pot is heated by the same fire that works the still. The crude 

 sulphur is placed in the pot, where it melts, and by. raising a plug, which closes the 

 tubulature, may be made to enter the still. The pipe forming the tubulature rises a 

 short distance above the bottom of the iron supply-pot.. This is in order that any 

 heavy mechanical impurities may sink to the bottom, and not enter the still, and 

 unnecessarily clog it. If the pot be always kept full of melted sulphur, and the latter 

 is permitted to enter by raising the plug, it is evident that no air will find its way 

 into either the retort or condenser. It is exceedingly important that this should bo 

 the case, because violent explosions are liable to occur if the highly-heated vapour of 

 sulphur comes in contact with an oxidising medium, such as atmospheric air, which 

 would convert it into sulphurous acid. The melted sulphur which collects on the 

 floor of the chamber is allowed to flow out when desired, by moans of an iron plug 

 attached to a rod of the same metal. The sulphur is not allowed to run out out iivl y, 

 so as to permit air to enter, for the reason stated above. The loss occurring during 

 the purification is owing partly to oxidation, resulting in the formation of sulphurous 

 acid, and partly to the fixed impurities contained in the crude material. See also tha 

 article SULPHUR. 



Preparation of the Charcoal. Of the throe ingredients of gunpowder, the most 

 important is generally considered to bo the charcoal. Unfortunately the woods which 

 are best adapted for the production of pyroligneous acids are not fitted for the manu- 

 facture of gunpowder; the charcoal must, therefore, bo prepared specially. T!i 

 following are the essential properties of good charcoal fur powder : 1. It .should l>o 

 light and porous. 2. It should yield little ashes. 3. It should contain little moisture. 

 Tho woods yielding good powder-charcoals are black alder, poplar, spindle tree, Mack 

 dogwood, and chestnut, Hemp-stalks aw said to yield good charcoal for gunpowder. 



