[ 273 ] 



gkfs, and 5,25 remained in the filter; 123 grains of the foda gave 

 out 20,91 of fixed air, and, as I afterwards found, kept about a 

 a grain of the lime in folution, now 21 grains of fixed air are ab- 

 forbed by 23,44 of limerthis then was the quantity of lime taken up 

 by the acid contained in 50 grains offal ammoniac, that is, 21,37 

 real marine acid, whereas by my calculation, fince 100 grains 

 marine acid take 118,3 °f lime, 21,37 fhould take up 25,28, the 

 diftv^rence is 1,84 grains, and even this I believe to proceed from 

 the whole of the fal ammoniac not having been decompofed, 19,8 

 grains of the acid appear to have been taken up by the lime, and 

 about 3,6 of the am.moniac efcapcd decompofition, this alfo clearly 

 appears by t')e adi n tf the foda, for 100 grains of this foda con- 

 tain 22 of mere alkali, then 123 grains of it contains 27 ; as 100 

 grains mere mineral alkali take up 73,41 of marine acid, then 27 

 fhould take up 19,82. 



Hence we fee that in Rigour 100 parts fal ammoniac may 

 be decompofed by ico parts chalk, for 100 parts chalk gene- 

 rally afford 42 of fxed air, and confequently contain 51,3 of 

 lime, and 100 parts fal ammoniac contains 42,75 real acid, and 

 fince 100 grains real marine acid are faturated by 118,3 of lime, 

 42,75 of this acid req are but 49,57 of earth ; but in all fuch cafes 

 the medium of decompofition.,is always taken in greater quantity 

 than is abfolutely requifite, otherwife the mixture would never be 

 perfe(Jt, and in this cafe part of the fait might fublime without de- 

 compofition ; hence 200 parts chalk arc moll commonly ufed. 



Vol. VII. , Mm though 



