7 REAGENTS. 



If tissue containing inulin is placed in glycerin, the inulin 

 separates out in the form of sphaero-crystals. Kraus has used the 

 same agent as a test for sugar. Iodine glycerin is used largely a,s 

 a medium for the study of protein granules. The reagent is made 

 by dissolving a little iodine in some glycerin in which has been 

 placed a little iodide of potassium. Glycerin is often used as a 

 clearing fluid and is especially good as applied to Hanstein & 

 Russow's methods. (See Poulsen, Botanical Micro-Chemistry.) 



Hydrochloric Acid. 



This is a valuable macerating agent for woody tissues. It is 

 also used to distinguish between oxalate and carbonate salts. The 

 former when treated with the acid dissolve without, and the latter 

 with effervescence. Pringsheim has used the acid as a test for 

 hypochlorin, a compound of chlorophyll bodies. The tissue to be 

 treated is sectioned and placed directly in the acid, where it is 

 allowed to remain 2 or 3 hours. The hypochlorin will separate out 

 in the form of brown spherical masses which later become needle 

 shaped crystals. Hydrochloric is also used in connection with 

 nitric acid as a cleaning mixture. 



Iodine. 



Iodine is one of the most useful agents in micro chemistry. It 

 is used in solutions of glycerin, alcohol, or an aqueous solution of 

 iodide of potassium, the latter being the one usually employed in 

 most tests. Dilute solutions generally give the best results and 

 the reaction is not obscured by the intense color of the reagent. 

 One quite well adapted for most tests is made by dissolving 1 gram 

 of iodine and 5 grams of potassic iodide in 100 c. c. of water, yet 

 even for some purposes, a solution of one-half this strength is 

 desirable. Iodine is sparingly soluble in water and in cases where 

 the effect of the pure agent is to be observed, it is better to put a 

 little metallic iodine in water under the cover glass at the side of 

 the preparation. In a solution of zinc chloride, iodine forms the 

 so called Schulze's reagent, which is very generally used as a test 

 for cellulose. Iodine is an infallible test for starch, coloring it in 

 the presence of water a rich blue. If the reagent is too strong, the 



