soap is then transferred to the ordinary wooden oriron frames (in the latter case surrounded withmatting, so that the soap may not cool too quickly).The above proportions yield 212 cwts. of soap.
Silicated Soaps. — Many varieties of soap aremet with in commerce termed silicated soaps. Theyare produced either by the addition of. silica itselfor an alkaline silicate to the soap paste, just beforecooling and solidification.
Soaps are also thus styled which contain pipe-clay,fuller’s earth, &c. These ingredients are reducedto powder, mixed with their own weights of drysoda ash or pearl ash, and thoroughly incorporatedwith the soap by crutching or stirring, while it isstill in the state of paste. The mixing must becompleted before the pasty soap cools.
Sand Soaps .—Sand soaps differ from silica soaps,inasmuch as in the latter the admixture has beenprepared artificially, while in the former commonwhite sand is the silicious ingredient, and the onlypreparation it has undergone is finely sifting. Inthe preparation of sand soap, the finely-sifted sandis added to ordinary white soap and thoroughlyincorporated with it while in the pasty condition, inthe proportion of 7 or 8 per cent.; and as soon asthe mass has cooled, it is taken from the frame andcut into tablets or moulded into balls.
When the silicious ingredient is flint or quartz,the calcined material is reduced to nearly an impal-pable powder by wet grinding with horizontal stones.The powder obtained is thinned out with about 20per cent, of water, and then boiled with caustic sodalyes of the strength above-mentioned for eight hours,or until it becomes a homogeneous mass. In thiscondition, in which it is technically termed detergentmixture , it is ready to be mixed with the soap paste.
Gossage's Process .—Of the three silicated soaps,the first that claims mention is that invented byW. Gossage. It consists in the introduction intosoaps prepared from fatty or resinous materials ofa highly concentrated solution of silicate of alkali.The process for the preparation of this silicate,termed also soluble glass, is described in the specifi-cation as follows :—When soda is used as the alkalinesolution to be combined with silica, 9 parts of sodaash containing 50 per cent, soda are mixed with 11parts of clear sand, and the mixture fused in areverberatory furnace, provided with a tap-holethrough which to allow the finished product to runoff. Sufficient heat is to be applied to the mixture,stirring from time to time until combination hasbeen effected; the product is then drawn, andreceived either in metallic moulds, or in mouldsformed of damp or moistened sand. The chargefor a furnace having a bed or sole measuring 60square feet, is about a ton of the mixed sand andalkali, and each charge requires four or five hoursto be properly fused and combined. For the pre-paration of silicate of potassium the proportions areequal weights of crude carbonate of potassium andsand, and these are melted exactly as in the pro-duction of silicate of sodium. It is always desirableto use such proportions of alkali and sand for the
production of the silicate, that the latter may bealmost wholly soluble in water; when the alkali isdeficient, however, this is not the case, and toobtain perfect solution it is necessary to use as thesolvent a solution of caustic soda or potash.
The solution of the perfect silicate may be effectedsimply by grinding the latter to powder, and agitat-ing this in a pan containing boiling water; but amuch preferable method of dissolving is by theemployment of an apparatus consisting of a vesselformed of iron plates, or other suitable materials,which vessel is fitted with a perforated diaphragmor false bottom placed about mid-way between topand bottom. The silicate, first broken into smalllumps, is placed upon the false bottom, and hotwater is introduced into the vessel to a sufficientheight to cover the pieces of glass to be dissolved.Steam is then introduced into the water so as tomaintain the latter at a high temperature.
As the glass dissolves, it communicates additionalgravity to the water, and the heavier solutiondescends in the vessel whilst the lighter fluid rises,and coming in contact with the glass also dissolvesit, and acquiring density again descends. In thismanner a continued circulation of the fluid takesplace, and the glass becomes nearly all dissolved,yielding a strong solution.
After allowing undissolved matters to deposit, thesolution is transferred to a cast-iron evaporatingpan, and by the application of heat concentrateduntil of specific gravity 1-450, when it becomesviscous on cooling, and is then in a condition to beadded to the soap. When the solution of the silicais to be added to a soda soap, the latter, preparedin the usual manner, is to be transferred from thecaldron into a tub or pan, termed the mixingvessel, capable of containing about 14 cwts. of soap,and the viscous solution of silicate of soda is to beadded in such proportions as to yield the particularquality of soap desired to be produced; and themixture is then well agitated by means of crutchesor paddles. The soap and the viscous solutionshould be each at such a degree of heat that themixture, when formed, may be at a temperatureof 160° Fahr., and the agitation is to be continueduntil the temperature is reduced ten degrees, thatis, to about 150° Fahr. The mixture is then trans-ferred to the cooling frames, and agitated thereinby means of crutches, until it becomes of suchconsistence as to render its continuance no longerpracticable.
For admixture with soft soap, the soluble glassis formed by the fusion of a mixture of sand andpotash, as previously mentioned, for the preparationof a silicate of potassium. This is dissolved, andafter concentrating the solution to the viscous con-dition, it is mixed with the soft soap, exactly asdescribed in the case of soda or hard soaps. As theproportional amount of alkali contained in a mixtureof soap with soluble glass is greater than that con-tained in the unmixed soap — if it is desired toreduce this amount, as the excess of alkali may beinjurious for some purposes to which the soap may