Reagents 37 



MISCELLANEOUS REAGENTS 



Canada Balsam is used almost exclusively for mounting. Very 

 thick balsam is disagreeable to handle and makes unsatisfactory 

 mounts. Very thin balsam, in drying out, allows bubbles to run 

 under the cover. Xylol is cheaper than balsam, and consequently 

 the balsam on the market is likely to be too thin for immediate use. 

 The stopper may be left out until the balsam acquires the proper 

 consistency. Material cleared in clove oil or cedar oil. may be 

 mounted directly in xylol balsam. It is not necessary that the clear- 

 ing agent should be also the solvent of the balsam. 



Paraffin should be of at least two grades, a soft paraffin melting 

 at 40 to 45 C., and a hard paraffin melting at 52 to 54 C. 

 Griibler's paraffin and most imported paraffins melt at the tempera- 

 ture indicated on the wrappers. The melting-point indicated on the 

 wrappers of paraffins sold by some American dealers does not enable 

 one to make even a guess as to the real melting-point. One promi- 

 nent optical company sells a paraffin marked 70 C., which usually 

 melts at 52 to 55 C. The fact that the price rises with the melting- 

 point may explain the discrepancy. 



Paraffin may be used repeatedly. Keeping it in the liquid con- 

 dition in the bath month after month is an advantage, since it 

 becomes more and more tenacious and homogeneous. 



Glycerin, glycerin jelly, Venetian turpentine, and gold size are 

 described in the chapter on "The Glycerin Method ' : (chap. vii). 

 Celloidin is described in the chapter on "The Celloidin Method' 1 

 (chap. x). The reagents already described are noted further in con- 

 nection with specific applications. Reagents used in making micro- 

 chemical tests are described in the chapter on "Temporary Mounts 

 and Microchemical Tests" (chap. v). 



A list of reagents with suggestions in regard to quantities and 

 prices will be found in chap. xxix. 



