[ 220 ] 



adly. We may now explain and do juftice to the_/?fy? experiment 

 of Mr. Wenzel on this fubjed. He difiolved 240 grs. of clean oyfter 

 fhells in his fpirit of nitre, and precipitated the lime contained in 

 them by dilute vitriolic acid, he then evaporated the whole, firft to 

 drynefs and afterwards by gentle ignition to expel the excefs of acid, 

 and laftly expofed the felenitic mafs to a more intenfe heat for one 

 hour, then weighing it in the fame vefTel found the felenite to 

 weigh 309,75 grs. 



application. 



The 240 grs. of purified oyfter Ihells contained 126,72 grs. of 

 lime, which I prove thus, he tells us p. loi, that 81 grs. of the 

 fame oyfter fhells gave out during folution 35 grs. of fixed air, 

 confequently 100 grs. would give out 43,2 ; now we have already 

 feen that 45 grains of fixed air denote the prefence of 55 of real 

 calcareous earth in 100 parts aerated lime, therefore 43 2 denote 

 52,8 of lime and therefore 240 parts of thefe fhells contained 

 126,72. 



Now as to the acid, fince 100 parts lime take up 143. 126,72 

 fhould take up 181,20 and the felenite being fo ftrongly heated 

 fhould weigh only the fum of both ■y.z : i8r,20+ 126.72 = 30792 

 or 308, grains which wants only 1,75 of the weight found by 

 Wenzel, this increafe found by him 1 impute to fome phofporatcd 

 lime originally in the fhells, the acid of which was not expelled 

 in the above experiment. 



Wenzel 



