GRENACHER'S MIXTURE FOR EYES OF ARTHROPODS. 297 



579. Nitric Acid has -a similar action. PARKER (Bull. Mus. 

 Comp. ZooL, Cambridge, U.S.A., 1889, p. 173; see Zeit. f. wiss. 

 Mik., viii, 1, 1891, p. 82) says that for eyes of scorpions the 

 usual 5 to 10 per cent, solutions are not strong enough. He 

 treats sections, fixed to the slide with Schallibaum's medium, 

 for about a minute with a solution of up to 50 per cent, of nitric 

 .acid in alcohol, or, still better, with a 35 per cent, solution of 

 a mixture of equal parts of nitric and hydrochloric acid in 

 alcohol. To make the solution, the acid should be poured 

 slowly into the alcohol (not vice versa), and the mixture kept 

 cool. 



580. Peroxide of Hydrogen (Oxygenated Water) (POUCHET'S 

 method, M. DUVAL, Precis, &c., p. 234). Macerate in- glycerin 

 to which has been added a little oxygenated water (5 to 6 

 drops to a watch-glass of glycerin). (Oxygenated water may 

 be procured from perfumers or hair- dressers, by whom it is 

 sold as a hair dye under the name of " Aureoline," " Golden 

 hair-wash," or the like.) 



The brownish-green colour communicated to tissues by 

 chromic solutions may be changed to yellow by means of oxy- 

 genated water (see 30). 



Osmium preparations may be bleached in the same way. 



581. Eau de Labarraque. Eau de Javelle (see 556, 557). These 

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

 Journ. de Microgr., 1887, p. 154, or Journ. Roy. Mic. Soc., 1887, p. 518. 

 It is, shortly, as follows : 8 parts of caustic soda are dissolved in 100 parts 

 of distilled water, and chlorine is passed through to saturation. During the 

 passage of the chlorine the solution must be surrounded with a mixture of 

 salt and ice, otherwise the temperature rises, and chloride and chlorate of 

 soda are produced. The resulting solution contains 7'45 per cent, of hypo- 

 chlorite of soda. It is green ; and the more effectual the cold, the greener is 

 the colour. The energy of the decolourising action is proportional to the 

 greenness of the solution. Of course the method cannot be used for bleach- 

 ing soft parts which it is desired to preserve. 



582. Chloroform helps to clear strongly pigmented chitin, 

 and combined with nitric acid will decolourise it entirely 

 (see below, in the chapter on Arthropods, Part II). 



583. GRENACHER'S Mixture for Eyes of Arthropods and other 

 Animals (Ahli. nat. Ges. Halle-a.-S., xvi; Zeit. f. wiss. Mile., 

 1885, p. 244). 



