APPENDIX. 361 



the solutions, but in most cases this is not of much 

 importance. 



Chromic acid. Dissolve 5 grms. in a litre of water, 

 from this the '3 and *2 p.c. solutions which are more 

 frequently used can readily be prepared. 



A little chromic acid may often be added with advan- 

 tage to potassium bichromate and ammonium bichro- 

 mate solutions ; it may also be used mixed in various 

 proportions with picric acid. 



Chromic acid hardens the tissues by an action analo- 

 gous to tanning ; but renders them, if they are left 

 in it too long, brittle and friable. 



Chromic acid and spirit. Mix two parts of chromic 



acid J p.c. with 1 part of methylated spirit (Klein), 

 or 



Mix equal parts of chromic acid *3 p.c. and alcohol 



50 p. c, 

 These solutions may require to be filtered before they 



are used, they should be kept in the dark. It is 



better to make them when required. 



Erlicki's fluid. Dissolve 2-5 grms. of potassium 

 bichromate and -5 grm. cupric sulphate in 100 c.c. 

 water. This is sometimes useful when a quicker 

 hardening agent than the chromium compounds 

 alone is required; after two days the fluid with the 

 tissue may be kept at about 40 C. to increase the 

 rate of hardenin. 



. 



Extraction of salts from bone. 



The bone should be divided into small pieces and 



