478 Intelligence and Miscellaneous Articles. 



2. Coagulated white of egg, treated with dilute sulphuric acid, 

 disengages a gas which sensibly discolours lead paper. 



3. Coagulated white of egg, brought into contact with a solution 

 of acetate of lead, becomes of a light brownish tint. 



The yolk of egg, under the circumstances above described, does 

 not act upon the salts of lead. 



Thus the discoloration of silver, by the action of eggs which have 

 been heated, is owing to the reaction of the sulphuret, formed by the 

 combination of the sulphur of the albumen on the soda which it 

 contains. — Joum. de Ckem. et de Pharm., Novembre 1850. 



ON A TEST FOR PROTEIN COMPOUNDS. BY M. E. MILLON. 



The very acid solution which is obtained by dissolving mercury in 

 its weight of nitric acid containing 4^ equivalents of water, is an 

 extremely sensible reagent for all albuminoid substances, and for a 

 considerable number of secondary products which are connected 

 with it. 



This nitromercurial solution communicates a red colour of consi- 

 derable intensity to these several substances, and it is easy thus to 

 ascertain the presence of l-10,Q00dth of albumen, and even a 

 smaller quantity. 



To give a direct idea of the delicacy of this reagent, and perhaps 

 of the advantage which may be taken of it in studying the organism 

 of vegetables, the author states that cotton, various kinds of starch, 

 and gum-arabic, when put into contact with it, assume a very di- 

 stinct rose tint. Urines are almost immediately coloured rose-red ; 

 after the nitromercurial solution has been added to them, and the 

 mixture having been heated, the urea is destroyed. 



The albumen of the blood and of vegetables, fibrin, casein, gluten, 

 legumin, silk, wool, feathers, horn, the epidermis, gelatin, chondrin, 

 protein, crystallin, the cornea, &c, are rendered of a more or less 

 intense red colour by this solution. 



When protein becomes soluble by the prolonged action of alkaline 

 solutions, or by that of sulphuric acid, the same colour is always 

 produced, but no insoluble matter is obtained ; the solution becomes 

 of a deep red colour, without yielding any precipitate. 



Xanthoproteic acid, the chlorites of protein, and the oxides of 

 protein derived from them, separate from the preceding products ; 

 they are not at all coloured red. This reagent exhibits differences 

 which it is very interesting to examine. The author has already 

 ascertained, that, by the action of chlorine upon albumen till the gas 

 ceases to be absorbed, there are formed no less than three substances 

 very distinct from each other. 



The nitromercurial solution is prepared by adding to the metal an 

 equal weight of nitric acid, containing 4^ equivalents of water ; reac- 

 tion takes place rapidly in the cold ; when it has become moderate, 

 the solution is to be very gently heated till the metal is completely 

 dissolved ; at this point there are to be added to one volume of the 

 mercurial solution two volumes of water. After some hours the 

 liquid portion is to be decanted from the crystals of nitrate and ni- 

 trite of mercury. This solution reacts in the cold on albuminoid 



