14 



it has not a constant composition. The mean of several analyses of a 

 portion taken from the centre of a large piece gave, — 



Calculated. Found. 



ZnO, . . . 73-021 .... 73-1 



CO2, . . . 14-838 .... 15-1 



HO, . . . 12-140 .... 11-8 



99-999 100-0 



The calculated percentage is derived from the formula 8ZnO,3C02, 

 6II0. Exposed to the air for three months, its composition was found 

 to be : — 



Calculated. Found. 

 ZnO, .... 75-277 .... 74-73 

 CO2, .... 13-597 .... 13-81 

 HO, .... 11-124 .... 11-45 



99-998 100-09 



The calculated numbers are here derived from the formula 3ZnO, 

 C05,2H0, which they assign to it. 



The following are the results of an analysis of a ball of hydrocarbo- 

 nate, made by M. Terrell : — 



ZnO, 6815 



CO2, 13-17 



CaO, 1-60 



AlA.FeA, 0-80 



HO, 12-40 



Hygroscopic water, 3-13 



Organic matter containing nitrogen, . . traces 



99-25 



This corresponds, according to him, to the formula 5ZnO, 2CO2, 3H0 5 

 but as part of the water is hygroscopic, he prefers the formula 3ZnO, 

 C02,2HO. If we deduct the lime, alumina, iron, and hygroscopic 

 water, and calculate the composition of the remainder in 100 parts, and 

 also calculate the theoretical composition in 100 parts from the formula 

 3ZnO,Co2,2HO, we get the following numbers : — 



Calculated. Found. 



3ZnO^ . . . 75-277 . . . 72-716 



CO2, . . . 13-597 . . . 14-052 



2H0, . . . 11-124 . . . 13-230 



99-998 99-998 



* Equivalent of Zinc = 32 -6. 



