100 



MICROSCOPIC TECHNIQUES 



lamps (.4) such as those manufactured by Hanovia Chemical Co. 

 or the H3 or H4 lamps of General Electric Co. or Westinghouse 

 Electric Co. 



The ultraviolet radiation is passed through a filter (F) to screen 

 out visible light. A variety of filters may be used for this purpose. 



The Corning color glass filter No. 584 

 ( new No. 5840) may be used in combina- 

 tion with a 5-10% copper sulfate solu- 

 tion, to which a drop or two of sulfuric 

 acid has been added, contained in a 

 quartz or other cell transmitting ultra- 

 violet rays. The copper sulfate solution 

 may be replaced by a Corning glass filter 

 No. 428 (4308), but the latter does not 

 remove the heat rays as well as does the 

 solution, and cannot be adjusted to com- 

 pletely absorb red light. Other filters 

 that may be employed are a combination 

 of the Shott glass filters UG2 and BG14, 

 the Corex filter of nickel oxide glass, or 

 the Uvet glass filters with a copper sul- 

 fate solution. 

 The filtered ultraviolet radiation practically free of visible light 

 is directed into a substage condenser (QC), made of quartz or ultra- 

 violet-transmitting glass, by means of a reflector (R) consisting of 

 either a quartz prism, a polished mirror of aluminum-magnesium 

 alloy, or, if the ultraviolet intensity is great, the usual plane micro- 

 scope mirror. Of course, w^hen the apparatus is aligned either 

 vertically or horizontally on a single optical axis, the reflector is 

 omitted. In those instances in which the fluorescence is generated 

 by the longer wavelengths of ultraviolet radiation, as is the case for 

 vitamin A, it is often possible to employ the ordinary substage 

 condenser, rather than one made of quartz or special glass, since the 

 usual grade of optical glass does not absorb much of the radiation 

 in this range. The condenser may be eliminated entirely if radiation 

 of lesser intensity can be used. Of the three most common forms of 

 condensers, the aplanatic gives the best results, although the Abbe 

 is generally quite satisfactory; achromatic condensers reduce the 

 intensity of the radiation due to the absorption of their many lenses. 



Fig. 3. Diagram of apparatus 

 for fluorescence microscopy. 



