BY COMPRESSION. S89 



fufion, in imitaition of what we conceive to have taken place preventing all 

 •„,«„_„ calcination, and 



'" "^^"'^«- . . perfeaiy fufing 



It was likewife important to acquire the power of retaining the carbonate, 



all the carbonic acid of -the carbonate, both on account of the 

 fa6t itfelf, and on account of its confequences ; the refult be- 

 ing vifibly improved by every approach towards complete fa- 

 turation. I therefore became anxious to inveftigate the caufe 

 of the partial calcinations which had always taken place, to 

 a 'greater or lefs degree, in all thefe experiments. Thequef- 

 ti'on naturally fuggefts itfelf. What has become of the car- 

 bonic acid, feparated in thefe partial calcinations from the 

 earthy bafis ? Has it penetrated the veflTel, and efcaped en- 

 ' tirefy, or has it been retained within it in a gafeous, but 

 highly comprefled ftate ? It occurred to me, that this quef- 

 tion might be eafily refolved, by weighing the velTel before 

 and after the action of heat upon the carbonate. 



With iron, a conftant and inappreciable fource of irregula- By experiment it 

 rity exifted in the oxidation of the barrel. But with porce- .^'n Wis ^''^ 

 Iain the thing was eafy; and I put it in practice in all my ex- vitiated the re- 

 periments with this material, which were made after the quef- ' 

 tion had occurred to me. The tube was weighed as foon as its 

 muzzle was clofed, and again, after the breech had been ex- 

 pofed to the fire; taking care, in both cafes, to allow all to 

 cool. In every cafe, I found fome lofs of weight, proving, 

 that even in the beft experiments, the tubes were penetrated 

 to a certain degree. 1 next wiflied to try if any of the 

 carbonic acid feparated, remained within the tube in a gafeous 

 form; and in that view, I wrapt the tube, which had juft 

 been weighed, in a flieet of paper, and placed it, fo furround- 

 ed, on the fcale of the balance. As foon as its weight was 

 afcertained, I broke the tube by a fmart blow, and then re- 

 placed upon the fcale the paper containing all the fragments. 

 In thofe experiments, in which entire caicinaiion had taken 

 place, the weight was found not to be changed, for all the 

 carbonic acid had already efcaped during the adion of heat. 

 But in the good refults, I always found that a lofs of weight 

 was the confequence of breaking the tube. 



Thefe facls prove, that both caufes of calcination had ope- With porcelain 



rated in the porcelain tubes ; that, in the cafes of fmall lofs, ^^^,'^ '*^'s c'ufe 



part of the carbonic acid had efcaped through the veflel, and exi'ited^abng^ 



that part had been retained within it. I had in view methods with the efca|)e 



Vol. Xlil.—SuppLEMENT. Ee j^^ of the acid. 



