The Paraffin Method 107 



Various clearing agents are in use. Xylol is the most generally 

 employed, and for most purposes it seems to be the best. Bergamot 

 oil, cedar oil, clove oil, turpentine, and chloroform are used for the 

 same purpose. Cedar oil and chloroform may, in some cases, be as 

 good as xylol. 



Only a small quantity of the clearing agent is necessary, enough 

 to cover the material being sufficient. 



The transfer from absolute alcohol to the clearing agent should 

 be gradual, like the hardening and dehydrating processes. The most 

 successful workers have been making this transfer more and more 

 gradual. Twenty years ago it was customary to transfer from 

 absolute alcohol directly to xylol; then a mixture of equal parts of 

 absolute alcohol and xylol was interpolated; in the second edition 

 of this book three grades were placed between the absolute alcohol 

 and xylol. It is undoubtedly better to make the transfer still more 

 gradual. The following series seems to be safe: 2J, 5, 10, 15, 25, 50, 

 75, and 100 per cent xylol. These mixtures of absolute alcohol and 

 xylol can be made with sufficient accuracy without measuring in a 

 graduate. The 50 per cent grade is made by mixing equal parts of 

 absolute alcohol and xylol; the 25 per cent, by adding to the 50 per 

 cent an equal volume of absolute alcohol; make the 10 per cent grade 

 from the 25 per cent by adding a little more than an equal volume 

 of absolute alcohol; in the same way, make the 5 per cent from the 

 10 per cent, and the 2J per cent from the 5 per cent. The different 

 grades may be kept in bottles and may be used repeatedly. 



About 3 or 4 hours is enough for each grade. The pure xylol 

 should be changed once or twice. Throughout the dehydrating and 

 clearing it is a good plan to keep the material in No. 4 shells, which 

 are made from glass tubing about 25 mm. in diameter. 



Other clearing agents may be used, but the process must be just 

 as gradual. 



THE TRANSFER FROM CLEARING AGENT TO PARAFFIN 



This should also be a gradual process. The most convenient 

 method is to place a small block of paraffin in the pure clearing agent 

 with the material, but the block of paraffin should not rest directly 



