CHEMICAL SCIENCE. 179 



a very minute portion of albumen in water may be detected. To 

 give an idea of the delicacy of this reagent, and to show its applica- 

 bility to the study of vegetable organization, it may be stated that 

 starch and gum acquire by its action a very distinct rose-color. 

 Urine almost always becomes of a rose tint after the nitro-inercurial 

 solution has been mixed with it, and the mixture been warmed. The 

 albumen of the blood, that of plants and fibrine, gluten, legumine, 

 silk, wool, feathers, horn, epidermis, and gelatine are equally affected. 

 This mercurial solution is more readily prepared by dissolving mer- 

 cury in its weight of nitric acid in the cold. When reaction has 

 ceased, a gentle heat may be applied to facilitate the solution of 

 metal. When the solution is complete, the liquid should be diluted 

 with two parts of distilled water by measure, and after some hours 

 the liquid is to be decanted from any mixed crystals of nitrate and 

 nitrite of mercury which may subside. This reagent acts on albu- 

 minous substances at low temperatures, but not so completely as at 

 a temperature of from 140 to 150 Fahrenheit, and it is even pre- 

 ferable to continue the application of heat to the boiling point. The 

 prolonged action of the reagent in excess does not alter the red mat- 

 ter, as has been ascertained by the contact of albumen with this so- 

 lution for over a year. According to M. Millon, this singular prop- 

 erty of giving a pink or red color to albuminous substances resides 

 neither in the nitrate nor in the nitrite of mercury, nor in their mix- 

 ture. It is necessary that there should be hyponitrous acid in the so- 

 lution which contains the two salts. The pure pernitrate of mercury 

 saturated with hyponitrous acid forms a delicate reagent, but inferior 

 to that of a saturated solution of the mixed salts. One or two drops 

 of this solution are sufficient for the detection of albumen, which has 

 been thus detected in the liquid of cholera when nitric acid and heat 

 have failed to demonstrate its presence. 



TO DETERMINE THE QUANTITY OF PHOSPHORIC ACID IN SOILS. 



THE Journal of the Franklin Institute translates from the Comptes 

 Rendus for Jan. 22 the following " Method of Determining the 

 Quantity of Phosphoric Acids in Soils by Means of a Normal 

 Liquor." This method is based, first, upon the property possessed 

 by solutions of potassa and soda of transforming, at a boiling tem- 

 perature, insoluble phosphates into the soluble phosphates of these 

 bases ; and secondly, upon the property possessed by nitrate of silver 

 of precipitating these phosphates, by forming a phosphate of silver, 

 which is the more easily and clearly deposited, as the precipitation is 

 more nearly complete, which allows the moment when the reaction has 

 ceased to be readily determined. The following is the manner of oper- 

 ating. The phosphoric acid of the compound to be examined having 

 been precipitated in an insoluble form, a known weight of these insolu- 

 ble salts is boiled with four times its weight of carbonate of soda, dis- 

 solved in from eight to ten times its bulk of distilled water. The liquid 

 is filtered to separate the insoluble carbonates and other salts, and the 



