Sulphate of Barytes. 219 



the charcoal it gives out but little caloric ; and on the other 

 hand, to the ditiiculty of imparting a certain degree of heat 

 to a mixture into which a large quantity of a body that is so 

 bad a conductor of heat a? charcoal enters. To remedy the 

 first of these defects, I had alread;. proposed to increase the 

 proportion of charcoal a little, and to incorporate with the 

 mixture of charcoal and sulphate of bar)-tes a twentieih of 

 nitrate of potash. To remedy the second, Mr. Goettling 

 advises to add muriate of soda to the mixture, which serves 

 at the same time as a conductor of heat and a flux. The 

 folio .\ ing is his method : 



Four parts of native sulphate of barytes in fine powder 

 are to be mixed with one part of muriate of soda and half a 

 part of charcoal powder. This mixture is to be pressed hard 

 into a Hessian crucible, and exposed for an hour and half 

 to a red heat in a good wind-furnace. After it has grown, 

 cold, the mass is to be reduced to a coarse powder, and 

 boiled for a inomtnt with sixteen parts of water. The, li- - 

 quor is then to be tiltered, and kept in well stopped bottles. 

 The time of exposure to heat may be shortened to one 

 half, if the quantity of muriate of soda be doubled, and the 

 matter occasionally stirred. In this case, too, double the 

 quantity of water should be used to lixiviate the mass. 



To prepare muriate of barytes with this lixivium of sul- 

 phurel of barytes, which at the same time holds in solution, 

 muriate of soda, muriatic acid is to be added in separate 

 portions till sulphurated hydrogen gas is no longer extri- 

 cated. The liquor is then to be filtered, a little hot water 

 is to be poured on the residuum, and the liquor is to be 

 evaporated to a pellicle. The lixivium being then filtered 

 afresh, is to be set to crystallize ; tlie muriate of soda, w hich 

 is much more soluble in water than the muriate of barytes, 

 and not more soluble with heat than without, is not depo- 

 sited by cooling, and the muriate of barytes crystallizes 

 alone. 



The remaining lixivium is to be evaporated and set to 

 crvstallize agrain, and this is to be repeated till no more 

 crystals of muriate of barytes. are formed. 



The barytic salt thus obtnined, if care be taken not to 

 employ an excess of muriatic acid, is perfectly white, on 

 account of the hvdro-sulphurct, by which the iron and 

 other metallic substances are precipitated. To be more 

 certain that it contains no muriate of soda, the different 

 products of the crystallization should be mixf-d together, 

 iissoivcd, and re-crystallized. 



XXXIV. Re- 



