[Footnote 5: See TINGRY'S _Painter's and Varnisher's Guide_. 1803.]
[Footnote 6: Take two pounds two ounces and a half of borax, and one
pound of acetate of lead, dissolve each in at least a pint of hot water,
mix together the two solutions, and allow the precipitate to subside.
Pour off the supernatant liquor as soon as it is clear, add some fresh
water (rain water is preferable) to the precipitate, and agitate. Then
pour the precipitate, whilst it is distributed throughout this last
addition of water, upon a filter of white blotting paper, and when the
water has passed through the filter, add more water. These fresh
additions of water must be repeated three or four times, merely for the
purpose of washing away all traces of the liquor which was retained by
the first precipitate, and which was formed by the first admixture of
the two solutions. The precipitate, when well washed, is to be placed in
a Hessian crucible, and exposed to a red heat for half an hour. A clear
glass will be formed; which must be reduced to a very fine powder.]
[Footnote 7: "As the very peculiar property which a saturated solution
of borax possesses, of uniting so readily with oil in any proportions,
has never yet been noticed by chemical writers, I experimented with its
constituents, boracic acid and soda, separately, with a view to
determine whether the results were to be attributed to the acid, to the
alkaline base, or to the particular salt formed by their union.
"One hundred parts of borax may be said to consist of:--
Parts
Boracic Acid, 35.80
Soda, 16.85
Water, 47.35
Consequently, 24 fluid ounces of water, holding in solution 1 ounce
(avoirdupois) of borax, will contain about 4.16 per cent of borax, or
0.702 per cent of soda only.
"I first tried the effect of a saturated aqueous solution of boracic
acid with linseed oil. They would not unite. I then prepared some
caustic soda by boiling a solution of carbonate of soda with quicklime,
decanting the clear caustic liquor, evaporating in a silver crucible,
re-dissolving in alcohol, and then distilling the spirit, and heating
the residual pure soda to redness. Even in this state, soda contains 23
per cent of water, and only 77 per cent of _pure anhydrous soda_.
"Ten grains of this soda were dissolved in 1000 grains of distilled
water. But as 10 grains of this soda contained only 7.7 grains of
_anhydrous soda_, the 1000 grains of water would contain just 0.770 per
cent of soda--a quantity that differs very little from that contained in
the saturated aqueous solution of borax.
"Seven measures of the soda solution were added to four measures of
linseed oil. This mixture differed so little in appearance, that it
might have been mistaken by any casual observer as identical with that
produced by a similar proportion of the solution of borax. It had,
however, a more soapy odour; and a considerable separation of its
constituent parts occurred almost immediately after agitation. This
separation increased for many days. The lower liquid was of a foxy brown
colour, and, after a week's repose, it amounted to 38 parts out of 59.
The upper 21 parts were white and saponaceous. I tried other proportions
of soda solutions with oil, but none resembled the results obtained from
solutions of borax with oil.
"Fancying that solutions of the bi-carbonate of soda might be more
analogous to those of the bi-borate of soda in their effects upon oil,
than solutions of caustic soda, I tried many mixtures of solutions of
the bi-carbonate with oil; but they were all dissimilar, in appearance,
odour, and properties, from like mixtures prepared with the bi-borate of
soda."--_Letter from C. Thornton Coathupe, Esq., on Vehicles for
Pigments. Published in the Art Union of February_ 1832.]
[Footnote 8: We are greatly multiplying artists, by "the promise to the
ear," and by our Art-Unions; whether we are like to have such returns to
the Commissioners of the Income-tax as those we have quoted, as a
consequence of our forced and hot-bed encouragement, remains to be seen.
Lord Brougham objects to the railroad mania, on account of the beggary
to be induced when the employment they give rise to is over. When the
ferment of patronage shall again have settled down to a selection of a
few favourites, may we not entertain somewhat similar fears?]