He states that during the American war, when the price of resin soap reached a high price, sodium silicate was much used as a substitute in soap making. The soap is found to be the more active and durable in proportion to the amount of silica in the silicate.
Schnitzer made a series of experiments in order to discover a mixture which, on fusing, will yield a silicate as rich as possible in silica, without being insoluble in boiling water, and he found the following proportions yielded on fusion the best silicate for the above purposes:—
100 parts of soda ash (containing 91 per cent, of Na2CO3), and 180 of sand. In the solution of silicate obtained on treatment with boiling water, the proportion of the Na2O to the SiO2 would then be as 1 to 2·9.
After long boiling with water, there ordinarily remains a slimy residue, which, on boiling up with fresh dilute soda-lye for a long time, furnishes a concentrated solution of silicate. This residue, consisting of silica, with insoluble higher silicates, was boiled with soda solution at 6° Baume, and the solution concentrated to 40° Baume, when the proportion therein of Na2O to SiO2 was found to be as 1 to 1·, and on cooling those crystallised out, sodium silicate of the formula Na2SiO3 ×
8H2O, in white foliated crystals.
On the small scale the perfume is generally added to the soap melted in a bright copper pan by the heat of a water bath; on the large scale it is mixed with the liquid soap, at the soap-maker’s, before the latter is poured into the frames.
The following are examples of a few of the leading toilet soaps:[174]
[174] See also Savonettes.
Soap, Bitter Al′mond. Syn. Savon d’amande, Fr. Prep. From white tallow soap, 56 lbs.; essential oil of almonds, 3⁄4 lb.; as before.
Savon au Bouquet. [Fr.] Prep. From tallow soap, 30 lbs.; olive-oil soap, 10 lbs.; essence of bergamot, 4 oz.; oils of cloves, sassafras, and thyme, of each 1 oz.; pure neroli, 1⁄2 oz.; brown ochre (finely powdered), 1⁄2 lb.; mixed as the last.