REAGENTS AND MOUNTING MEDIA. 479 



shavings are now shaken free of the discoloured alcohol and steeped 

 in a new supply, and allowed to remain for several days, being fre- 

 quently stirred. This fluid is then filtred, and evaporated down 

 until a fragment of very coarse unbleached blotting-paper moistened 

 with it, and subsequently with hydrochloric acid, quickly becomes a 

 deep violet colour. The residual fluid thus obtained is brown, and 

 smells like camphor. Preserve in a well-closed bottle. Reagent 

 for lignin, 79. 



Chloral-hydrate. Used as a clearing reagent, of which it is one of the best, 

 especially for growing points and pollen-grains. A solution of 8 

 parts in 5 parts water. 



Chloroform. Solvent of fat and etherial oils. 



Clilorophyll solution, freshly prepared and concentrated ; a reagent for cork 

 and cuticle, 185. 



Chlorzinc iodine (Iodized chloride of zinc). Zinc is dissolved in pure hydro- 

 chloric acid, and the solution evaporated (metallic zinc being kept 

 in it during the process) to the consistence of strong sulphuric acid ; 

 in this is dissolved as much iodide of potassium as it will take up, 

 and finally as much metallic iodine as it will dissolve. Chlorzinc 

 iodine is the simplest reagent for cellulose, but acts much more 

 rapidly in watery than in alcoholic sections, hence the latter should 

 be placed in water. Glycerine sections can be placed in it, as the 

 reagent diffuses very rapidly in glycerine. 



and iodine. Dissolve iodine in chlorzinc iodine till a precipitate 

 begins to be formed. This fluid stains the callus of sieve-plates a 

 deep brown colour. 



Chrom-acetic acid, 1 per cent. Chromic acid 0*7 per cent., acetic acid O3 



per cent, in water. Used for " fixing " alga?. Time taken, up to 



twenty-four hours. See p. 248. 

 Chromic acid, 1 per cent. For fixing Xitella, filamentous algae, etc. Twelve 



to twenty-four hours. After alcohol, the best of the simple fixing 



reagents, and preferable to it for many purposes. 



20 per cent. Used in preparing siliceous skeletons, pp. 96, 258. 



25 per cent. Dissolves membrane of pollen-grains. 



Concentrated. Used as a macerating agent like Schultze's fluid, 

 to which it is, however, inferior. Does not dissolve cork, 186. 



(All tliese Chromic Acid solutions are in Water.) 

 Chromosmium acetic acid (Flenmiing's Fluid), prepared of varying strengths 



of chromic, osmic and acetic acids, and probably the finest of all 



fixing fluids. See pp. 248, 438 and 444. 

 Cloves, Oil of. Used for clearing sections prior to mounting in Carfada 



balsam, etc. Preparations must be thoroughly dehydrated before 



using it. 



Coaguline, for sticking card labels on micro-slides. 

 Cohris normal solution, a culture fluid for certain bacteria, made of 1 gramme 



acid phosphate of potassium, 1 gramme sulphate of magnesia, 2 



