286 Cross and Hillebrand—Cryolite from Colorado. 
Taking the figures in the third column and combining the 
fluorine with the calcium, sodium, potassium, and, as far as 
possible with the aluminium, there remains of the latter 5°32 
per cent, requiring 4°66 per cent of the oxygen, an amount 
agreeing very closely with that obtained above by difference 
and making the sum total almost exactly 100. 
22°30 Ca requires 21°18 F. 
0°10 Na ? 0°08 
0°04 Ka * 0°02 
9°99 Al a 20°79 
9°98 Al,O; ‘ 42°07 
15°46 H,O 
42°07 F 
99°94 
nation, in the case of a hydrated fluoride, if no precaution was 
taken to prevent the escape of fluorine. 
Substituting in the mean of analyses a and d for sodium and 
potassium their equivalent of calcium, and dividing the percent- 
ages by the atomic weights, the atomic ratio is found to be as 
given below : 
Al 15°31 —+ 27°4 = 0°559 
Ca 22°41 + 40 = 0°560 
H,O 1546 =—18 <= 0°859 
O 466 — 16 = 0291 
F 42°07 +19 = 2°214 
The ratio of Al:Ca:F is here nearly as 1:1:4, the same 
as found by Hagemann. Subtracting from the atomic value for 
water, an amount 0-291 equal to that for oxygen, in order to 
form with the latter hydroxyl, the result is as given under I, 
while under II appears the ratio referred to calcium as unity. 
L I. 
Al 0°559 1-00 
Ca 0°560 1-00 
H,O 0°568 1-01 
