40 FIXING AND HARDENING AGENTS 



50 per cent, alcohol, to which is added at the instant of using a little 

 acetic acid, 5 or 6 drops per 100 c.e. 



To make the solution, add the finely powdered salts to the alcohol in 

 excess, and leave them together in total darkness, for twenty-four 

 hours. 



Fix for twelve to twenty-four hours in the dark. Then treat with 

 strong alcohol for twelve to twenty-four hours. 



61. Dekhuyzen's Liquids (C. R. Acad. Sci., cxxxvii, 1903, pp. 415 

 and 445). (a) 250 c.c. of 2-5 per cent. sol. of bichromate in sea-water, 

 25 c.c. of 6-3 per cent, nitric acid, and 54 c.c. of 2 per cent, osmic acid. 

 For general use with marine animals. 



(b) 173 1 c.c. of the bichromate sol. and 26-9 of 2 per cent. sol. of 

 osmic acid. 



For objects containing calcareous elements that it is desired to 

 preserve. 



These liquids are stated to be isotonic with sea-water. 



62. Bichromate and Sublimate (Kultschitzky, Arch. f. 7nik. 

 Anat., xlix, 1897, p. 8). Two grm. bichromate, | grm. corrosive 

 sublimate, 50 c.c. 2 per cent, acetic acid, and 50 c.c. 96 per cent, 

 alcohol. The mixture should be filtered after twenty-four hours. 

 Tissues of vertebrates may remain in it for four to six days. 

 Lavdowsky {Zeit. wiss. Mik., xvii, 1900, p. 301) takes 500 c.c. 

 of 1 per cent, acetic acid, 20 to 25 grm. bichromate, and 5 to 10 

 c.c. saturated solution of sublimate in water. See" Zenker, § 78. 



63. Bichromate of Ammonia. This salt is in considerable favour 

 for hardening. Its action is very similar to that of the potassium salt. 

 Fol says that it penetrates somewhat more rapidly, and hardens some- 

 what more slowly. It should be employed in somewhat stronger 

 solutions, up to 5 per cent. 



64. Neutral Chromate of Ammonia is preferred by some. It is used 

 in the same strength as the bichromate. Klein has recommended it for 

 intestine, which it hardens, in 5 per cent, solution, in twenty-four hours. 



65. Bichromate of Calcium. Sonnenbrodt (Arch. mikr. Anat., 

 Ixxii, 1908, p. 416) fixes ovaries of Gallus in 20 parts of 2 per cent, 

 sol. of calcium bichromate with 10 of 2 per cent. sol. of sublimate and 

 1 of acetic acid. 



66. Bichromates and Alcohol. Mixtures of bichromate of potash 

 or ammonia with alcohol may be employed, and have a more rapid 

 action than the aqueous solution. Thus Hamilton takes for hardening 

 brain a mixture of 1 part methylated spirits with 3 parts of solution of 

 Miiller ; see also Kultschitzky's Mixture, ante, § 60). Preparations 

 should be kept in the dark during the process of hardening in these 

 mixtures. 



67. Sulphurous Acid. Waddington (Journ. Roy. Mic. Soc, 1883, 

 p. 185) uses a saturated solution of sulphurous acid in alcohol for fixing 

 infusoria. Overton (Zeit. wiss. Mik., vii, 1890, p. 9) uses the vapours 

 of an aqueous solution for fixing algae. 



