EAU DE JAVELLE 299 



seems, however, that in the presence of lignified tissues the 

 reaction may fail, even when nitrates are present in abundance. 

 Diphenylamine is also used to distinguish between crystals of 

 asparagin and potassium nitrate. Asparagin dissolves without 

 color in this reagent, while potassium nitrate assumes a deep 

 blue color on dissolving in it. 



Eau de Javelle. — ^Prepared by adding to an aqueous solution 

 of chloride of lime a solution of potassium oxalate so long as a 

 precipitate is formed. The solution is then filtered and diluted 

 somewhat with water before using. Or 20 parts of a 20 per 

 cent, solution of calcium chloride is diluted with 100 parts of 

 water, and after this has stood for some time, a solution of 15 

 parts of pure potassium carbonate in 100 parts of water is added. 

 If a film should form on the surface of this on exposure to the 

 air, a few drops of the solution of potassium carbonate should be 

 added and the precipitate filtered away. 



Lignin is extracted from sections of woody tissues which 

 have lain in the eau de Javelle solution for some time, and there- 

 after, on treating with chloroiodide of zinc, the membranes 

 show only a cellulose reaction, staining only purple with the 

 chloroiodide of zinc. 



Starch grains included in chloroplasts may be demonstrated 

 by first treating sections, or even whole leaves, with eau de Javelle 

 until the chloroplasts are dissolved (this may take from one to 

 twenty-four hours), and then treating the material with a solution 

 of potassium iodide-iodine. The starch grains will take oil a 

 blue or violet color. In some cases, however, the starch grains 

 themselves are dissolved with the eau de Javelle. In such cases, 

 and indeed in most cases, chloral hydrate and iodine is to be 

 preferred for demonstrating starch inclusions in chloroplasts 

 (see under this head). 



When the forms of the cells simply are to be studied, eau de 

 Javelle is very useful in clearing the sections by dissolving the 

 cell-contents. If the sections become too clear in the eau de 

 Javelle, this defect may be corrected by treating the sections 

 with alcohol or with a solution of alum. See under Cyanin for 



