BY DR. LAUDER BRUNTON. 429 



may be considerably larger than the other ; place one on each 

 pan of a pair of scales, and add shot or weights to the pan 

 containing the lighter beaker till the other is counterbalanced. 

 Pour into the smaller beaker a little mercury, and into the 

 other the same weight of nitric acid (sp. gr. 1,042). Dissolve 

 the mercury in the nitric acid at first without, and afterwards 

 with gentle warmth. Pour the solution into a graduated glass 

 measure, and add to it twice its volume of water. Let H stand 

 for some hours, and then decant the fluid from the crystalline 

 deposit. 



/ 



SECTION II. ALTERATION OF ALBUMIN BY ALKALIS. 



Egg albumin is converted into alkali-albuminate when it is 

 dissolved in caustic potash or soda, or when they are added to 

 its solutions. Alkali-albuminate is the substance first described 

 by Mulder under the name of protein. He considered it to be 

 the essential part of all albuminous bodies, and regarded them 

 as compounds of it. 



Albuminous bodies are not converted immediately into 

 alkali albuminate, but they undergo this change when allowed 

 to stand with caustic alkalis, and it is greatly accelerated by 

 the application of heat. 



Alkali albuminate is not coagulated by heat. It is soluble \ 

 in weak alkalis. 'It is precipitated when the alkaline solutions I 

 are neutralized by acids. It is soluble in very dilute acids, ' 

 especially hydrochloric acid, and when the acid is added in ( 

 excess to an alkaline solution, the precipitate which was , 

 thrown down by its neutralization is again dissolved very/ 

 readily by the acid. When the acid solution is neutralized/ 

 by an alkali the albumin is again precipitated. 



If the alkali albuminate is precipitated by neutralization, 

 and the precipitate immediately dissolved in acid, it is quickly 

 converted into syntonian. If it is precipitated, and allowed 

 to stand for some time, it will still be dissolved by dilute 

 acids, but not so readily as immediately after precipitation, 

 and it must be warmed with them to 60 C. in order to convert 

 it into syntonian. 



If alkaline phosphates are present in the solution, alkali 3 

 albuminate is not precipitated by neutralization. When just 

 sufficient acid has been added to a solution of alkali albumi- 

 nate to convert the basic phosphate into acid phosphate, the 

 slightest excess of acid, or even C0 2 will produce a precipitate. 

 In studying the action of alkalis on albumin, it is as well to 

 begin with their action on solution of albumin, and afterwards 

 to examine the solid alkali albuminate. 



** 13. Alkali Albuminate. Dissolve some albumin in 

 water in a beaker ; add to it a few drops of liquor potassse, and 



