248 CORROSION, DECALCIFICATION, AND BLEACHING. 



CHAPTEK XXIV. 

 CORROSION, DECALCIFICATION, AND BLEACHING. 



Corrosion. 



527. Caustic Potash, Caustic Soda, Nitric Acid. Boiling, or 

 long soaking in a strong solution of either of these, is an effi- 

 cient means of removing soft parts from skeletal structures 

 (appendages of arthropods, spicula of sponges, &c.). 



528. Eau de Javelle (Hypochlorite of Potash) (NOLL'S METHOD, 

 Zool Anzeig., 122, 1882, p. 528), Noll remarks that the 

 usual method of preparing the skeleton of siliceous sponges 

 and similar structures by corroding away the soft parts by 

 means of caustic potash has many disadvantages, of which a 

 principal one is that the spicula are not preserved in their 

 normal positions. He therefore proceeds as follows : A piece 

 of sponge is brought on to a slide and treated with a few drops 

 of eau de Javelle, in which it remains until all soft parts are 

 dissolved. (With thin pieces this happens in twenty to thirty 

 minutes.) The preparation is then cautiously treated with 

 acetic acid, which removes all precipitates that may have 

 formed, and treated with successive alcohols and oil of cloves, 

 and finally mounted in balsam. 



The same process is stated to be applicable to calcareous 

 structures. I feel convinced, however, that if the structures 

 are delicate, they will suffer, or be entirely, destroyed. 



529. Eau de Labarraque (Hypochlorite of Soda) may be used 

 in the same way as eau de Javelle. LoosS (Zool. Anz., 1885, 

 p. 333) finds that either of these solutions will completely 

 dissolve chitin in a short time with the aid of heat. For this 

 purpose the commercial solution should be taken concentrated 

 and boiling. A formula for making it is given in 548. 



