APPARATUS 



*e. Chlor-zinc-iodine (Schulze's solution) may be pur- 

 chased ready prepared from the dealers in 

 micro-chemical reagents ; or it may be prepared as 

 follows : 



(1) Dissolve no grms. of zinc in 300 c.c. of pure 

 hydrochloric acid, and evaporate to 150 c.c. (sp. 

 gr. about i'8). 



(2) Dissolve 12 grms. of KI in as little water as 

 possible : add 0*15 grm. of iodine. 



(3) Mix (i) and (2), and filter, if necessary, through 

 asbestos. The solution should have a dark 

 sherry-brown colour. 



*f. Solution of aniline chloride : a saturated solution is 

 made in distilled water, filtered, and a few drops of 

 hydrochloric acid added so that it may give a 

 distinctly acid reaction. The solution should be 

 colourless. 

 *g. A solution of common salt : a 5 per cent, solution, 



i.e. 5 grms. of salt to 100 c.c. distilled water. 

 Many other reagents besides these will be required for the 

 work described below ; also substances for permanent mount- 

 ing and sealing up of slides : their preparation and uses are 

 detailed in the Appendix A. 



Care should be taken 'in the preparation of the reagents : 

 they must be kept pure, and should be renewed occasionally. 

 Glass rods with rounded ends are to be used for removing 

 drops of the reagents from the bottles to the slide, and the rod 

 should always be cleansed before dipping it into a reagent-bottle. 

 *24. Two wash-bottles such as are in ordinary use in a 

 chemical laboratory : the one should contain alcohol (methyl- 

 ated), the other distilled water. 



