414 Scientific Proceedings, Royal Dublin Society. 
Then we have :— 
Cal. 
Heat necessary to raise 80-0 grms. of HF through 1°C.= 80-0 x °346 = o7-7 
£ i. 2080», | Sik 5)! 9 = 1908-0). -oter ame 
: ee ae 60-0 a $102 ,, 59 = 60 & C183 = 11°3 
Ee CERO) oe EON 4, 6, SOG ta Ated 
a 3 »,  846°6 », products - 582°5 
Heat necessary to raise 846°6 grms. of products from 
20-100° = 582°5 x 80 = 46600°0 
i.e. heat generated by solution of 180 grms. of Siz (Amorphous) in 362 HF > 46600-0 © 
” ” 2 99 oe) 39 ”9 oy 258°9 
and ,, absorbed in warming thas Me », trom 20°-1425°> 281-0 
, Me ; de ness me », along OEF SS Herd) 
ie ‘ by solution of 1 ,, », (Quartz) in HF (Fremy) = 0-0 
- ii in warming er op >, trom 20°-1425° 
(Pionchon) = 404-6 
E ni Ks in fusing aes a ,,  at1425° (Latent 
Heat) > 135°3 
im warming 1 se a », along OBF > 539:9 
Thus we arrive at the remarkable number 135:3 calories 
as a safe minimum value for the latent heat of quartz. How 
much greater it may be we cannot at present say. As I have 
said, the specific heat of amorphous silica is probably greater 
than that of quartz. If we assume that it has the same mean 
value as quartz from 0° to 1425° we obtain the much greater value 
258°9 as the minimum latent heat for quartz. 
The above serves as an example of how we may arrive at the 
latent heat of any mineral, with a high degree of probability, by 
means of two determinations of specific heat, and two determina- 
tions of the heat of solution. ‘The latter are at present difficult 
in the case of the silicates on account of their slowness. But the 
difficulty should not be insurmountable. 
In conclusion, I have to express my indebtedness to Professor 
C. V. Boys, F.R.s., and to Professor W. A. Shenstone, F.R.s., for 
much valuable information about fused silica. ‘To several of the 
Professors of the Royal College of Science for Ireland I am 
very deeply indebted. 
