52 CHAPTER V. 



true platinic chloride, or tetrachloride^ PtOl^, but the com- 

 pound HjPtClg, that is, platinochloric, or hydro-ohloro- 

 platinic acid, by custom called platinum chloride. It occurs 

 as brown-red crystals, easily soluble in water and very 

 deliquescent. For this reason it had better be stocked in 

 the form of a 10 per cent, solution, kept in the dark (weak 

 solutions — 0'5 per cent. — may be kept in the light). 



It appears that some authors have stated that they were 

 using platinous chloride, PtCl^, but that is not possible, as 

 this salt is not soluble in water. 



Rabl {Morph. Jahrb., x, 1884, p. 216) employed an 

 aqueous solution of TSOO. The objects remained in it for 

 24 hours, and were then washed out with water. Well- 

 washed preparations give good chromatin stains with the 

 " basic " tar colours ; but I find, as do others, that plasma- 

 staining with the " acid " colours is rendered extremely 

 difficult. It causes a certain shi-inkage of chromatin. 



It is now almost always employed in the form of mixtures. 

 For these see §§ 44, 45, 49, 76, as well as the mixtures given 

 under Piceic acid and Foemol. 



76. Rabl {Zeit. wiss. Mikr., xi, 1894, p. 165) takes for 

 embryos of vertebrates, and also for other objects, 1 vol. of 



1 per cent, platinum chloride, 1 of saturated sublimate, and 



2 of water. 



Lenhossek [Arch. Milcr. Anat., li, 1898, p. 220) takes 20 

 parts of 1 per cent, platinum chloride, 20 of 5 per cent, 

 sublimate, and 1 of acetic acid. 



77. Palladium Chloride (Schulze, Arch. mih. Anal., iii, 1867, p. 

 477). — Used by Schulze as a hardening agent in a 1 : 800 solution, 

 acidified with hydrochloric acid. 



Cattaneo has used it in solutions of I'SOO, 1-600, or TSOO strength, 

 for from one to two minutes, for Infusoria. 



Pkenkbl {Anat. Anz., viii, 1893, p. 638) recommends for connective 

 tissue a mixture of 15 parts 1 per cent, palladium chloride, 5 parts 2 per 

 cent, osmic acid, and a few drops of acetic acid. 



78. Iridium Chloride (EiSEN, Zeit. wiss. Mih., xiv, 1897, p. 195).— 

 Solution of one half or one fifth per cent., acidified with 1 per cent, of 

 glacial acetic acid. 



With the ovotestis of the snail, I have obtained about the worst fixa- 

 tion I have ever seen, but with the testis of Triton much better I'esults. 



79. Osmium Chloride (Eisen, /oinm.o/Jfor^/!..,xvii,1900). — Solution 



