tie Sulphirfoiis Acid.—Sulphiit of Pet-/ip>. 3iy 



The proponicns of principlea which conRitute the fulphites not havhig been yet deter- 

 jnined, we endeavoured to afcertain a method which might lead us as near as poffible to 

 tlie truth ; but it could not be applied to all the kinds of fulphite, on account of the difa- 

 greement of their properties ; fo that we were under the neceffity of employing feveral 

 methods. 



The Sulphite of Pot-ufJj-'] Sulphureous acid gas was pafTed into a faturated folution of 

 very pure carbonate of pot-alh, until the etTervefcence entirely ceafed. During this combi- 

 nation, a fmall quantity of caloric is difengaged, and the folution cryftallizes by cooling. 



This fait is ufually white and tranfparent ; fometimes it isflightly yellow and femi tranfpa- 

 rent, if its folution has been very concentrated, and the cryftallization confufed. Its tafle is 

 penetrating and fulphureous, its figure that of a long rhomboidal plate ; its cryftallization 

 often prefents fmall needles diverging from a common centre. 



When expofed to a fudden heat it decrepitates, and lofes its water of cryftallization 5 

 afterwards by ignition it emits fome vapours of fulphureous acid ; and at length a portion 

 of fulphuris feparated, and the refidue is fulphate ofpot-afli with a flight excefs of alkali. 



By cxpofure to air it flightly efflorefces, becomes opake and hard, its penetrating fulphu- 

 reous tafte difappears, and it acquires another, which is acrid and bitter. In this Rate it no 

 longer effervefces with acids. 



If this experiment be made in a clofed apparatus with oxygene gas, it is found that the 

 volume of the gas is diminiflied, and that it is even totally abforbed when the quantity is pro- 

 perly regulated. We fee therefore that the fulphite of pot-alh may be converted into ful- 

 phate by depriving it of a portion of its fulphur by fire, or by introducing a quantity of oxy- 

 gene at a low temperature. 



The fulphite of pot-a(h is foluble in a quantity of water nearly equal to its own mafs ; 

 and this folubility is increafed by heat. 



This fait is dccompofcd by lime and by barytes, as may be fliewn by pouring lime water 

 into a folution of the fulphite of pot-afh. A white precipitate is afforded, which is the ful- 

 phite of lime, and the pot-alh remains difengaged in the water. 



The fulphureous acid does not therefore follow the fame laws of aflinity as the fulphuric 

 acid, fince this laft adheres more ftrongly to pot-afli than to lime. 

 The alkalis do not change the nature of the fulphite of pot-afli. 



Among the acids, fome decompofe the fulphite of pot-a(h by feparating the fulphureous 

 acid ; others change its nature without driving off its acid, but by affording a portion of 

 oxygerie, and converting it into fulphuric acid. The firft of thefe effefls is produced by the 

 fulphuric, muriatic, phofphoric and fluoric acids; the fecondis cffeiled by the nitric and the 

 oxygenated muriatic acids. The acids of borax and of carbo do not occafion any change in 

 the cold. 



When the fulphuric acid is poured on the fulphite of pot-afh, a rapid effervcfcence takes 

 place with a crackling noifc, at the fame time that much caloric is difengaged. 



The nitric acid, on the contrary, emits red vapours, mixed only with a fmall quantity of 

 fulphureous acid, and the refidue is compofed of a mixture of the fulphate and nitrate of 

 pot-afh. 



The oxygenated muriatic acid mixed with the fulphite of pot-.>fh immediately lofcs its 

 fmcU, and tbc fluid is dcpriviid of its fulphureous taftc. 



If 



