ee sy 
G. J. Brush on Boltonite. ; 397 
No, 2 the portion insoluble in dilute hydrochloric acid was con- 
sidered to be pure boltonite, and from this was calculated the 
composition of boltonite as given in 1(a) and 2(a : 
But I have found by experiment that boltonite is acted* upon 
even by very dilute hydrochloric acid, and this being the case, 
the insoluble portion in v. Hauer’s analysis must have contained 
an excess of silica derived from the partial decomposition of 
boltonite by dilute acid. It is therefore evident that any con- 
clusions in regard to the composition of boltonite based upon 
the eo of this insoluble portion must be erroneous. This 
partial decomposition of boltonite also affords a satisfactory ex- 
planation of the excess of silica in v. Hauer's analysis over that 
obtained by Smith. 
Itis unnecessary to follow Kenngott farther, as I shall pro- 
teed to show from my own analyses the correctness of Smith’s 
conclusions. 
In the year 1854 I made an examination of boltonite, but not 
g entirely satisfied with the purity of the substance analyzed, 
analysis was not published. The mineral was separated from — 
the gangue by acetic acid and selected as carefully as possible. 
Fused with carbonate of soda it gave— 
Si Mf x iti 
4094 5084 i ed 0-27 eres 100°60 
rding the ignition, the result confirmed Dr. Smith’s anal y- 
%s, but I could not be certain that the mineral was perfec iy 
Sieur 4 — not until a few weeks since that sora oa 
rd kindly placed at my disposal a specimen containit 
large irr ar Snare of Briefs Hs which I have been able 
to select t € mineral pure for analysis. | | 
times ws in a magnesian limestone in crystals which are some- 
mes more than an inch in diameter; these irregular erystals im- 
lanted in the angue often present rectang sections, 
hee 4 very SaiAel  Glagwanie i one direction. The color of 
®Specimens I examined was dark ash ory bu pny re " 
i were almost colorless. It sera feldspar, and there- 
321. Bek - ote or a bes erie poke - tga eid 
*, “tore the blowpipe in platinum fo 
but the color changes io k htryellow; ith salt of phospho i 
&$ Teactions for silica ser iron. When treated with ited 7 é 
bydrocloric acid (i. ¢,, one part acid to ten parts cen Arse 
woo mineral j ially decomposed. In the quan 
re the isinerat yas first powerfully heated over a ot 
anal a subsequently decomposed by carbonate of soda. 
* Dr. Smith also alludes to this fact loc. cst. 
