ON STAINING FLUIDS, AND STAINING. 105 



Mix and add 



Glycerine (Price's best), 8 ounces. 

 Bichloride of Mercury, 1 grain. 



Mix thoroughly, and filter very carefully, 

 Sty rax. A liquid gum which exudes from the 

 bark of the Liquidambar orientate. This is 

 used specially for the mounting of diatomaceae, and 

 the method of its use will be described when, in the 

 chapter on " Mounting," full instructions are given 

 for cleaning and mounting these organisms. Styrax 

 is soluble in alcohol, ether, benzol, and xylol, which 

 last is its best solvent for microscopical purposes. 

 The solution should not be too thick, and must be 

 carefully filtered. Styrax is preferable to Canada 

 Balsam as a medium in which to mount diatoms, 

 its refractive index being greatly higher than that 

 of Balsam, whilst it is equally safe and durable. 



Monobromide of Naphthalin is soluble in 

 alcohol and ether ; its high refractive index- 

 double that of Canada balsam renders it a valu- 

 able mounting medium for diatomacese. The cover 

 should be " ringed " with wax before any cement is 

 applied to secure it. Then two coats of shellac 

 varnish, followed by white zinc cement, or, if the 

 slides are to be used with oil immersion objectives, 

 by the special cement of which the formula is given 

 amongst the 



CEMENTS. 



Dammar Varnish. Gum dammar, dissolved 

 in benzol, has been much used as a mounting 

 medium ; its only recommendation, however, is 

 that it is easy to apply. It is not safe, neither is 

 it durable, and the author strenuously advises that 



