Cross and Hillebrand—Cryolite from Oolorado. 275 
the oil bath, was used for heating. The sulphuric acid was 
obtained of the highest degree of concentration and purity by 
distillation from a platinum retort. The water was determined 
been heated in a tube with either oxide of lead or carbonate ot 
sodium, the results being the-same whether one or the other 
was used. 
The eryolite, of which the analysis is here given, possessed 
the specific gravity 2°972 at 24° C., was faintly pink in color, 
and contained as a visible impurity the oxide of iron repre- 
sented in the analysis: 
Fe,0; 0°40 
8 a 12°90 
Ree com y ha ase tye em a ema a 
Na 32°40 
HO 0°30 
eee 53°56+ 
99°83 
second analysis seemed unnecess ry. 
_ Alteration of cryolite—The alteration of the cryolite procéeds 
in two ways, producing the same minerals in the end. By 
one process the principal cleavage fissures are utilized by the 
solutions which effect the change, and thin walls are formed of 
Ae 4 network of partitions in the three directions of the chief 
cleavages of the original cryolite. These partitions or walls 
Proceeds from the neighborin uartz, and from the bounda- 
"es of the different crystalline individuals of the eryolite, the 
result being a compact crystalline mass of a faint bluish tinge. 
he material at hand illustrates the two processes and their 
* Annalen der Chemie, cexiii, p. 1. 
+ As the mean of 53°35, 53°46, 53°55 and 53°85. 
