APPENDIX OF FORMULAE, ETC. 



FIXING AND HARDENING REAGENTS 



CHROMO-ACETIC ACID SOLUTION. 



Chromic acid 1 gram. 



Glacial acetic acid -5 c.c. 



Water 98-5 



This solution is a good all-round fixative for plant material. 

 It can be used full strength for stems, leaves, buds, etc., but 

 must be diluted with equal quantities of water, or even 

 more for delicate objects such as algae. The length of time 

 for which the material should remain in the fluid depends on 

 the size of the object, in any case it should be several hours. 

 After fixing, the objects are placed in a muslin bag and 

 washed in running water for 6 hours, after which they are 

 passed through graded alcohols, 30%, 50%, 70% to 90%. 



CORROSIVE- ACETIC FLUID. 



Saturated solution of corrosive sublimate .... 100 c.c. 



Glacial acetic acid 5 c.c. 



After fixation wash in 70% alcohol to which a few drops 

 of tincture of iodine have been added, then wash in 70% 

 alcohol until all colour of iodine has been removed. Objects 

 can then be kept in this strength of alcohol until required for 

 use. 



PERENYI'S FLUID (Chromo-nitric Acid). 



Alcohol (92%) 3 parts 



Nitric acid (10%) 4 



Chromic acid (0-5%) 3 



Objects are fixed in this fluid for 5 or 6 hours, then treated 

 with 70% alcohol for 2 days, changing the alcohol frequently, 

 passed on to 92% alcohol for some days, and finally treated 

 with absolute alcohol for 2 to 3 days. 



HERMANN'S FLUID (Platino-aceto-osmic Acid). 



Platinic chloride 1% solution 15 parts 



Osmic acid 2% solution 4 ,, 



Glacial acetic acid 1 part 



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