32 FIXING AGENTS. 



CHAPTER V. 



FIXING AGENTS CHLORIDES, ORGANIC ACIDS, AND OTHERS. 



Chlorides. 



47. Bichloride of Mercury (Corrosive Sublimate). Corrosive 

 sublimate is stated in the books to be soluble in about sixteen 

 parts of cold and three of boiling water. It will probably 

 be found that the aqueous solution contains about 5 per cent, 

 of the sublimate at the temperature of the laboratory. It is 

 more soluble in alcohol than in water, and still more so in 

 ether. Its solubility in all these menstrua is augmented by 

 the addition of hydrochloric acid, ammonious chloride, or 

 camphor. With sodium chloride it forms a more easily 

 soluble double salt ; hence sea- water may dissolve as much 

 as 15 per cent., and hence the composition of the liquid of 

 Lang. 



For fixing corrosive sublimate may be, and very frequently 

 is, used pure ; but in most cases a finer fixation will be ob- 

 tained if it be acidified with acetic acid, say about 1 per cent, 

 of the acid. I find that a saturated solution in 5 per cent, 

 acetic acid is a very good formula for marine animals. VAN 

 BENEDEN has recommended a saturated solution in 25 per 

 cent, acetic acid. 



In either case, the most concentrated solution obtainable 

 should in general be taken. The cold saturated aqueous 

 solution will suffice in most cases; but for some very con- 

 tractile forms (coral polypes, Planaria), a concentrated solu- 

 tion in warm or even boiling water should be employed. For 

 Arthropoda the alcoholic solution is frequently indicated. 

 Delicate objects, however, may require treatment with weak 

 solutions. HARTING found solutions of 0*2 to 0'5 per cent, 

 suitable for blood-corpuscles, and PACINI'S fluids are much of 

 the same strength. For these see the chapter on Examination 

 Media. 



Objects should in all cases be removed from the fixing bath 



