T. L. (Islington). The ingredients referred to are all used by Le Gray, the originator of the waxed-paper process. They are supposed not only to increase the sensitiveness of the paper, but to add to its keeping qualities. We have no doubt that a letter addressed to the College of Chemistry will find the gentleman to whom you refer.
D. G. (Liverpool). It would be not only difficult but more expensive to prepare your own sulphuric ether; but we again assure that the best is to be procured at from 5s. to 6s. per pound, and wholesale at considerably less. You may satisfy yourself by a reference to our advertising columns.
F. H. D. Albumenized paper will keep many days after it has been excited with a forty-grain solution of nitrate of silver. We have used Whatman's and Turner's papers twenty days old, and with perfectly satisfactory results. The thin Canson is of all others most disposed to brown; but it is preferable to all others in use from the richness of the tints produced and its rapidity of printing.
Erratum.—Vol. viii, p. 546. l. 20. from bottom, for "burnishing" read "bruising."
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