76 BULLETIN OF THE BUSSEY INSTITUTION. 
solved out from the ashes by pure water. The results of these ex- 
periments are as follows: they were all made upon fine ashes that 
had been sifted through a sieve which had twenty-four meshes to the 
linear inch. 
To determine the amount of soluble silica, if any, contained in the 
ashes “in the free state,” 50 grammes of the ashes were boiled with 
a freshly made solution of carbonate of soda, which was subsequently 
filtered, neutralized with chlorhydric acid, and evaporated to dryness 
to render the silica insoluble. In one experiment one half of a solu-: 
tion, prepared by dissolving 50 grammes of the crystallized carbon- 
ate in 175 c. c. of water, was boiled with the ashes for half an hour, 
and after the clear liquor had been decanted the other half of the 
solution was poured upon the ashes and boiled in its turn for a similar 
length of time ; there was obtained 0.0474 per cent of “ free soluble 
silica.” In another experiment similar to the foregoing with the 
exception that the solution of carbonate of soda was half as strong 
as before, 0.0418 per cent of the free silica was observed. These 
amounts are, of course, insignificant. 
To determine combined soluble silica 50 grammes of the ashes were 
boiled with diluted chlorhydric acid prepared by mixing 50. c. of 
the concentrated acid with 100 c. c. of water. One half of this mix- 
ture was boiled upon the ashes for half an hour, the resulting solution 
was decanted, and the other half of the diluted acid then added and 
boiled for the same length of time. The washed residue was boiled 
with a solution of carbonate of soda, as in the trials described in the 
previous section, and an amount of silica equal to 0.88 per cent of the 
original ashes was obtained. To this must be added 2.18 per cent. of 
silica, which was dissolved by the chlorhydric acid and recovered 
' . therefrom by evaporation in the usual way. Hence the total soluble 
silica amounted to 3.06 per cent. 
In order to determine if the active silicate thus shown to be pres- 
ent in the ashes can combine readily with water, 150 grammes of the 
ashes were dried at 100° and weighed. 0.10 per cent of hygroscopic 
water was expelled. The dried ashes were then moistened thoroughly 
with water and again dried at 100°; a quantity of water amounting 
to 0.11 per cent .of the ashes taken was held-in combination. This 
combined water was not expelled on heating the ashes for some 
hours at 110°, nor at 150°; but at 200° it was driven off. 
