TRANSPARENT SOAP. 189 



alcohol. As to the' preservation of tissues, the mass is alka- 

 line, which is against it ; yet some workers still prefer soap 

 to paraffin,, and it has lately been recommended by so expe- 

 rienced a worker as Chun, for Siphonophora (certainly as 

 delicate a class of objects as any that exist), on the ground of 

 its producing less shrinkage than paraffin. 



289. Transparent Soap (POLZAM, Morph. Jalirl., iii, 1877, 

 3tes Heft, p. 558). The following account is taken from 

 Salensky's paper on the gemmation of Salpa (loc. cit.). 



Take good white soap (" gewohnliche Kernseife"), cut it 

 up into thin slices, and put them to dry in the sun for some 

 days until they become white. The slices are then to be 

 rubbed up to a fine powder, which is mixed with spirit to 

 the consistency of porridge. Now mix the porridge with 

 alcohol and glycerin in such proportions that the whole shall 

 contain, for every ten parts by weight of the soap, 22 parts of 

 glycerin and 35 parts of alcohol (90 per cent.). Let the whole 

 simmer until there is obtained a perfectly transparent, syrupy, 

 somewhat yellow fluid. 



The objects, previously dehydrated in alcohol, are imbedded 

 in this mass in the usual manner. 



The mass may be removed from the sections either by means 

 of water or of very dilute alcohol. 



290. Transparent Soap (KADYI, Zool. Anz., 37, 1879, vol. ii, 

 p. 477). Twenty-five grms. of shavings of stearate of soda 

 soap (any stearate of soda soap will do, but the most to be 

 recommended is the sort known in commerce as "weisse 

 Wachskernseife") are heated in a retort with 100 c.c. of 96 

 per cent, alcohol over a water-bath until the whole is dissolved. 

 Filter if necessary. If a drop of the solution be now poured 

 into a watch-glass it will be seen that it almost immediately 

 solidifies into a white mass. This is not what is wanted, and 

 is a sign that the solution does not contain water enough. 

 Small quantities of water are therefore added by degrees to 

 the solution, and the effect tested from time to time by pouring 

 a drop of the mixture into a watch-glass. The mass will be 

 seen to become more and more pellucid until a point is reached 

 at which it is almost perfectly transparent, with merely the 

 slightest blue opalescence. The preparation of the mass is 

 then complete. 



