14 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. 
[BULL. 167. 
order to gain evidence bearing upon their chemical structure. The 
evidence, at least, is of value, whether the interpretation of it be right 
or wrong. Each fact helps to the ultimate solution of the central 
problem, the problem of constitution. 
Pectolite. 
The pectolite which was chosen for examination was the well-known 
radiated variety from Bergen Hill, New Jersey. The mineral was in 
long, white needles, and apparently quite pure; but the analysis shows 
that it contained some carbonate as an impurity. Enough of the 
material was ground up to furnish a uniform sample for the entire 
series of experiments, and the work properly began with a complete 
analysis. The results obtained are as follows: 
Analysis. 
Si0 3 
ALO., .... 
CaO 
MnO 
Na .0 
Total H 2 
C0 3 
53. 34 
.33 
33.23 
.45 
9. 11 
2.97 
.67 
100. 10 
Fractional water 
At 105° 
0.27 
.16 
.22 
2.32 
At 180° 
At 300° 
At redness 
2.97 
All of the water was given off at a barely visible red heat; and th( 
figures show that practically all of it is constitutional, a fact whict 
perhaps hardly needed i everiflcation. The analysis gives the acceptec 
formula for pectolite, 
HNaCa 2 Si30 !t . 
Does this represent, as is commonly assumed, a true metasilicate 1 ?- I 
it does, we should expect that ignition would split off silica propor 
tional to the acid hydrogen, or one-sixth of the total amount. T< 
answer this question several portions of the pectolite were sharpb 
ignited, to complete dehydration, and then boiled each for fifteen min 
