254 . DECALCIFICATION 



BLEACHING 



611. Mayer's Chlorine Method {Mitth. Zool. Stat. Neapel, ii, 

 1881, p. 8). Put into a glass tube a few crystals of chlorate of 

 potash, add 2 or 3 drops of hydrochloric acid, and as soon as the 

 green colour of the evolving chlorine has begun to show itself, 

 add a few cubic centimetres of alcohol of 50 to 70 per cent. Now 

 put the objects (which must have previously been soaked in 

 alcohol of 70 to 90 per cent.) into the tube. They float at first, 

 but eventually sink. They will be found bleached in from a 

 quarter of an hour to one or two days, without the tissues having 

 suffered. Only in obstinate cases should the liquid be warmed 

 or more acid taken. Sections on slides may be bleached in this 

 way. Instead of hydrochloric acid, nitric acid may be taken, in 

 which case the active agent evolved is oxygen instead of chlorine. 



This method serves both for removing natural pigments, such 

 as those of the skin or of the eyes of Arthropods, and also for 

 bleaching material that has been blackened by osraic acid, and 

 according to renewed experiments of Mayer's, is to be preferred 

 to the peroxide of hydrogen method. 



For bleaching chitin of insects, not alcohol but water should 

 be added to the chlorate and acid (Mayer, Arch. Anat. Phys., 

 1874, p. 321). 



See also Mayer in Zeit. zciss. Mik., xxiv, 1907, p. 353 (paraffin sections 

 exposed to the vapour of chlorine water). 



Grynfeltt and Mestrezat (C. R. Sac. Biol., Ixi, 1906, p. 87) add 

 2 c.c. of 20 per cent, solution of chloric acid (HCIO]) to 15 c.c. of alcohol 

 and put sections (of retina) into it for several hours at 42° C. 



612. Eau de Labarraque. Eau de Javelle (see §§ 586, 587). These 

 are bleaching agents. For the manner of preparing a similar solution 

 see early editions, or Jotirn. de Microgr., 1887, p. 154, or Journ. Roy. Mic, 

 Soc., 1887, p. 518. Of course, the method cannot be used for bleaching 

 soft parts which it is desired to preserve. 



613. Peroxide of Hydrogen (Oxygenated Water) (Pouchet's 

 method, M. Duval, Precis, etc., p. 234). Macerate in glycerin, 

 to which has been added a little oxygenated water, 5 to 6 drops 

 to a watch-glass of glycerin. Solger {Centralbl. med. Wiss., 

 xxi, 1883, p. 177) takes a 3 per cent, solution of peroxide. Furst 

 (Morph. Arh. Schrvalbe, vi, 1896, p. 529) points out that after a 

 time it inacerates. 



The method serves both for removing pigments and for bleach- 

 ing osmic and chromic material. 



614. Peroxide of Magnesium (Mayer, Grundzuge, p. 290). Use as 

 chlorine, § 611. A slow but delicate method. 



615. Sulphurous Acid. Prof. Gilson wrote that he found 

 alcoholic solution of sulphurous anhydride (SOg) very convenient 

 for the rapid decoloration of bichromate objects. A few drops 



