(Copy-EBB) 
2517 Derby St., 
Berkeley, Calif., 
Aug. 21, 1925. 
Hr. Edward. B- Chamberlain, 
18 West 89th St., 
New York City. 
Dear Hr. Chamberlain:- 
1 received your letter inquiring about water glass but a few 
days ago, having just returned from my vacation, and what with my Deing 
busied with registration affairs since then, I hope you will be kind and 
forgive me for not answering you at least a few days sooner. 
The note which you saw in Science was submitted some nine 
months ago, about the time that water glass received its first serious 
attention. I know of only two instances in which it has been tried 
out quite extensively;- by one of the professors here at this University 
and by Professor biaisdell at Stanford. It was used successfully as 
something cheaper and quicker than Canada balsam. 
Another advantageous substitution is of glycerine jelly mounting, 
especially where a great deal of use of such mounts is made by students. 
Of course, cover slips are used, since any portion of the permanently 
exposed, hardened water g'lass will develop surface cracks. ,<hen the cover 
slips are used this cracking appears as a white etching at the edge of the 
slip- where it does no harm. Water glass doeqhot crystallize, since it is 
a super-cooled liquid. Its consistency, or strength, would be rather hard 
to determine inasmuch as I use a commercial, drug store preparation. It 
is sold here by the Owl Drug Company, of Ban Francisco under the trade name 
of Siliso, for about twenty cents a pint, and the directions on the outside 
recommend a dilution of one part of water glass to nine parts of water, 
in the preserving of hen's eggs. However, as a mounting agent, the exact 
strength of the commercial preparation seems to best . It is possible to 
use a dilution of as much as one half of v/ater. A thicker consistency than 
that as it is sold is harder to handle, and will harden exceedingly quickly, 
in a minute or so. The mounts do not absorb water from the atmosphere, 
but when immersed in water for three days or longer, it will dissolve, the 
cover slip and slide being recovered and as good as new. The actual mount 
becomes practically as hard as glass. 
Of course you are most interested in the possibility of its 
mounting mosses. Unfortunately I have not tried to mount mosses; but I 
feel that it would be well worth your trying, since it seems from your 
letter that you have not. I do not think that there is much danger of 
the collapsing that you speak about. Another suggested use of water glass 
is the preserving of leaves in a natural form, but a few feeble attempts 
have resulted in no success. I recently read an article in which it was 
stated that it was very good for painting raw tree wounds. 
This is about all that I can tell you. It is interesting to 
read up its chemistry in the usual textbooks of chemistry, which usually 
devote a paragraph or two to it. I hope that you may be successful. 
Very sincerely, 
(Sgd.) Dean Burk. 
