252 CORROSION, DECALOIFICATTON, AND BLEACHING. 



540. Phoroglucin (ANDEER, Centralbl. f. d. med. Wiss., xii, 

 xxxiii, pp. 193, 579 ; Intern. Monatschr., i, p. 350 ; Zeit.f. iviss. 

 Mik., 1885, pp. 375, 539; Journ. Roy. Mic. Soc., 188 7, p. 504). 



Andeer recommends a mixture of phoroglucin with hydro- 

 chloric acid. He takes, for bones of Batrachia, 5 to 10 per 

 cent, of acid ; for Chelonia and Birds, 10 to 20 per cent. ; for 

 Mammalia, 20 to 40 per cent. In these mixtures the bone is 

 decalcified in a few hours, becoming so soft that it has to be 

 subsequently hardened. 



Desilicification. 



541. Hydrofluoric Acid (MAYER'S method, Zool. Anz., 1881, 

 No. 97, p. 593). The objects from which it is desired to re- 

 move siliceous parts are brought in alcohol into a glass vessel 

 coated internally with paraffin (otherwise the glass would be 

 corroded by the acid) . Hydro-fluoric acid is then added drop 

 by drop (the operator taking great care to avoid the fumes, 

 which attack mucous membranes with great energy) . A 

 Wagnerella borealis may thus be completely desilicified in a 

 few minutes. Small pieces of siliceous sponges will require a 

 few hours or at most a day. The tissues do not suffer ; and 

 if they have been previously stained with acetic acid carmine, 

 the stain does not suffer ; at least, this was so in the case of 

 Wagnerella. 



This dangerous method is best avoided. As regards sponges, 

 I would point out that if well-imbedded, good sections may be 

 made from them without previous removal of the spicula. 

 The spicula appear to be cut ; probably they break very 

 sharply when touched by the knife. Knives are of course not 

 improved by cutting such sections. 



Bleaching. 



542. MAYER'S Chlorine Method (Mitth. Zool. Stat. Neapel., ii, 

 1881, p. 8). This is a process imagined for the purpose of 

 getting rid of the blackening that often occurs as a conse- 

 quence of treatment by osmic acid. 



The specimens are put into alcohol (either of 70 or 90 per 

 cent). Crystals of chlorate of potash are added until the 

 bottom of tin? vessel is covered with them. A few drops of 

 concentrated hydrochloric acid are then added by inrtms of a 



