Cross and Hillebrand—Oryolite from Colorado. 287 
It will be seen that by combining hydroxyl and fluorine the 
ratio Al: Ca: H,O:(F, OH) is 1:1:1:5 and the formula for 
the mineral becomes CaF,, Al(F, OH),, H,O, in which the 
fluorine and hydroxyl combined with the aluminium stand 
nearly in the proportion 2:1. Were the latter proportion ex- 
actly fulfilled, the formula might be written 3CaF,, 2AIF,, 
Al(OH),, 3H,O requiring the percentages : 
Al 15°36, Ca 22-42, F 42°60, O 4:49, H,O 15°13=100-00 
cannot, but must be water of crystallization. That a portion 
of the water is basic, is rendered more than probable by the 
fact that at 800° C. some is still retained. In this connection, 
the following experiments were made. 0°5677 gr. of the min- 
eral, not however from the same sample as that used for anal- 
ysis, dried first at 100° C. and contained in a platinum crucible, 
was exposed in an air bath during 145 hours to temperatures 
tanging from 100° C. to 800° C., the weight being taken at in- 
tervals averaging ten hours each. The results in brief showed 
that at 145° ©., the loss was but 0°35 per cent, at 230° C. only 
‘92 per cent, at 250° ©. 7-02 per cent, after prolonged heating 
at 265-270° C. 9-49 per cent, and at 295° C. 18-92 percent. As 
no further loss occurred after six hours’ heating at 295-300° C., 
# portion of the residue, which still retained its original appear- 
ance, was subjected to a quantitative test for water, of which 
176 per cent was found. This added to the 13-92 per cent 
dr tven off below 300° C. made the total 15°68 per cent. Since 
this is slightly higher than the mean of the previous results, it 
Seemed possible that some fluorine might have escaped. The 
remainder of the residue was therefore tested quantitatively 
for fluorine, of which was found 40°60 per cent, thus proving 
the correctness of the surmise. A similar experiment with the 
Same general results was made upon a smaller portion of an- 
other sample. A comparison of the ful] results of both experi- 
ments showed that by sufficiently prolonged heating at approxt- 
mately 270° C., all the water of crystallization could be driven 
off, also that by still further heating at little, if any, higher 
temperature, the basic water began to escape, but was not en- 
tirely expelled, even after many hours’ exposure to a temper- 
ature of 295-300° ©. 
In the Journal of the Chemical Society for 1888, page 140, 
Walter Flight describes a mineral obtained from the eryolite 
be ‘of Greenland. “It is made up of a congeries of minute 
white transparent crystals, mostly broken up and lying entan- 
