178 ACIDIFIABLE COMBUSTIBLES. 



tion of nepheline according to these supposi- 

 tions : 



(1.) 2-25 (atom of alumina) : 2 (atom of silica) : : 3373 



(alumina in mineral) : 29*98 



= silica unfted to the alumina. 

 (2.) 4 (atom of soda) : 3 (1 \ atom silica) : : 20-4,6 



(soda in mineral) : ... 15-345 



= silica united to soda. 



Total silica .... 45-325 



The silica in the mineral being only 44'11 

 grains, is less than the amount of the silica de- 

 duced from the above suppositions by 1^1 5 grain. 

 Let us admit the specimen analyzed by Arfwed- 

 son to have been perfectly pure, and the analy- 

 sis to have been accurate, and let us deduce 

 from it the atomic weight of silica. 



It is obvious that nepheline must consist of 3 

 integrant particles of silicate of alumina, united 

 to 1 integrant particle of sesquisilicate of soda. 

 Of consequence, id of the deficiency belongs to 

 the sesquisilicate of soda. Hence, silicate of 

 alumina, according to Arfwedson's analysis, is 

 composed of 



Gives Silica . 29-17 or 1-94582 



1-94582. Alumina . 3373 - 2-25 



The atom of silica deduced from this mineral 

 is less than when deduced from bucholzite. 

 The reason is, probably, that the substances with 



