230 SCIENTIFIC AMUSEMENTS. 



Toilet soaps of superior quality are frequently remelted and further 

 refined and perfumed, again cast into blocks, cut up into small 

 lumps, which are squeezed into the shape of tablets by machinery 

 acting on much the same principle as the presses used for striking 

 coins and medals (Expt. 2) ; some kinds are ground up in a " mill " 

 to a thick paste, and then formed into tablets by special machinery 

 instead of by remelting and casting, &c. 



Expt. 277. To obtain Glycerine from Soap Liquors. Glycer- 

 ine is prepared from the brines left in soap boiling by evaporating 

 them down, when salt is crystallised out (used over again for 

 salting out fresh batches of soap), and finally impure glycerine is 

 left, which is refined and purified by various processes before 

 becoming fit for use. Evaporate some of the brine from Expt. 

 276 to dryness over the steam bath, and then pour some strong 

 alcohol on the residue ; this will dissolve the glycerine, but only a 

 small portion of the salt ; filter the liquid and evaporate it again 

 until all the alcohol is driven off, taking care that the alcohol 

 vapour does not take fire (Expts. 40, 41). A small quantity of 

 glycerine mixed with a little salt will remain, from which most of 

 the salt can be farther separated by dissolving again in alcohol 

 and evaporating after filtering. 



Expt. 278. To make Transparent Soap. Cut up some lumps 

 of good yellow soap into shavings and expose them to the air in a 

 moderately warm room for some days, so as to get them as dry as 

 possible. Place the dry coarsely powdered shavings in a flask and 

 pour on strong alcohol (methylated spirit will do) to the extent 

 of three or four times the weight of the soap used. Place the 

 flask in a saucepan of water so as to form a waterbath (Expt. 89), 

 and connect a condensing arrangement (fig. 24) with the mouth of 

 the flask, so that when the water-bath is hot the alcohol vapour 

 formed from the boiling spirit in the flask may be condensed and 

 collected for use over again. The soap will gradually dissolve in 

 the spirit, which should be distilled off until but little drips from 

 the end of the condenser ; the thick treacly fluid then left in the 

 flask should be poured out into a mould (a small basin will answer) 

 and left to set for 24 hours ; on scooping out the mass from the 

 mould in a lump by means of a "spatula" or flexible painter's 

 knife (palette knife), it will be found to be more or less clear, like 

 badly strained jelly; by exposing it to the air for a long time 

 it will gradually dry up and harden, and become somewhat more 

 transparent. If a small quantity of glycerine be added to the 

 alcohol whilst dissolving the soap therein (about 1 part glycerine 

 to 1 5 or 20 of soap), the resulting product is generally clearer ; 

 soap thus clarified, made from a sound quality of stock soap in 



