Journal of Applied Microscopy. 323 



It is stated in the dispensatories that acetone is produced by the dry distilla- 

 tion of woods, acetates, gums, certain carbohydrates, etc., and has a specific 

 gravity ranging from 0.7920 to 0.800.S. It boils at from 56 degrees to 58 degrees 

 C. It has an empirical formula of C.^HgO, although constitutionally it is 

 Dimethyl-ketone, CO, CHg, CHg.' It is soluble in all proportions in water, 

 alcohol, ether, chloroform, and volatile oils, and dissolves pyroxylin, camphor, 

 fats, and many resins. 



Its action upon pyroxylin, with which this note has chiefly to deal, seems to 

 be more intense than the customary ether-alcohol mixture. It dissolves not only 

 the soluble-cotton form of pyroxylin, composed of the lower nitrates of cellulose, 

 but the true gun cotton or hexanitrate of cellulose, which the ether-alcohol 

 mixture cannot do. 



The collodion process has attained such an importance in histological 

 technique, that any modification in the way of abridging some of the numerous 

 steps, provided the good results are not interfered with, should be worthy of note. 



Fixative Action. — Acetone also possesses desirable qualities as a fixing, 

 hardening, and dehydrating agent, retaining to some extent the natural color of 

 some of the tissues ; so that a piece of tissue hardened in it may be placed in a 

 weak solution (4 per cent.) of acetone collodion, and then in a stronger solution 

 (8 per cent.), mounted upon a block and immersed in chloroform ; or if some 

 other fixing agent has been used the tissue may be placed in acetone to complete 

 the hardening and to prepare it for the collodion baths. 



In addition to the fixing and dehydrating properties of acetone, it seems also 

 to be useful as a solvent for many of the dyes used in histology. Further 

 experimentation is, however, necessary. Another feature, which may be of some 

 importance, is that the pyroxylin is very readily soluble in a mixture of equal 

 parts of acetone and ether, and the official collodion is also freely miscible with 

 the acetone collodion. 



A table comparing the acetone and alcohol methods is herewith appended. 

 If the fixing agent has been of an aqueous character, the process is lengthened. 



(i per cent. Collodion (official). 



X 



8 per cent. Acetone Collodion. 8 percent. Collodion (official). 



X X 



4 per cent. Acetone Collodion. Ether-alcohol. 



Dehydration Dehydration 



(strong acetone). (strong alcohol). 



Fixing Agent Fixing Agent 



(acetone 70 per cent). (alcohol 70 per cent). 



(To be read from below upwards.) 



In the commercial acetone a small amount of water or alcohol may exist as 

 impurities, and if this grade of acetone be used in making the collodion, the 

 collodion may become opaque and require a longer time to clear when placed in 



