52 ELEMENTARY CHEMICAL MICROSCOPY 



Either a carbon arc with special carbons or a mercury vapor 

 lamp may be employed as radiant. 



Fig. 23 shows diagrammatically the construction of a fluo- 

 rescence microscope. The rays from the radiant R are concen- 

 trated by the quartz condensing lens Q, then pass through the 

 Wood-Lehmann filter F consisting of a quartz or of a blue 

 "Uviol" glass cell, thence the rays pass to the reflecting quartz 



X 



FIG. 23. Reichert Fluorescence Microscope. 



prism P which in turn reflects them into the quartz lens dark- 

 ground condenser. This device brings the ultraviolet rays to a 

 focus upon the object supported upon the stage by means of an 

 object slide of quartz or of Uviol glass. Ordinary glass, besides 

 being practically opaque to rays of very short wave length, as 

 stated above, fluoresces with a violet or bluish tint under the 

 action of the ultraviolet rays and cannot therefore be employed 

 as a support. If it is necessary to cover the preparation ordi- 

 nary glass cover glasses may be employed, but it is unwise to do 

 so if thin quartz cover glasses are available. 



As in all dark-ground illuminators, an immersion fluid between 

 condenser and object slide is essential. In this case glycerine is 

 employed (n = 1.47). 



The light filter whose function is the removal of waves of 

 long wave length, affecting the eye as light, consists of two com- 

 partments, one filled with a 20 per cent copper sulphate solution, 

 the other with an aqueous solution of nitrosodimethyl aniline 

 (i: 12000). 



The only changes in construction and materials lie entirely 



