16 ORGANIC CONSTITUENTS. 



be reduced to a fine powder, and treated successively with etlier 

 and alcoliol. By these means we succeed in removing nearly 

 all foreign bodies from the albumen, which when dried exhibits 

 a white or pale yellow colour, is devoid of taste and odour, and 

 presents a neutral reaction. If perfectly dry, albumen in this 

 state may be exposed to a temperature of 213 without passing 

 into the coagulated condition. When digested in cold water, 

 it gradually swells up, and finally dissolves, forming a mucilagi- 

 nous, colourless, and insipid fluid, which on being heated to 140° 

 begins to give indications of coagulating : if the solution is 

 very dilute, the temperature may be raised to 165 with the 

 occurrence of this change, and when present in very small 

 quantity the albumen may not separate till the fluid boils, or 

 even until the ebullition has been prolonged for a short time. 



When albumen is analysed, it yields the same results as 

 protein in regard to carbon, hydrogen, nitrogen, and oxygen, 

 but it also contains a small quantity of phosphorus and sulphur, 

 (less than 1 o together,) which are absent in protein. According 

 to Mulder's analyses, i the albumen of eggs may be represented 

 by the formula C^„^ H.,^ N^^ O,^, SP + or 10 Pi^ + SP, which, as 

 we shall presently see, is identical with the formula for fibrin. 



The albumen of the blood differs from this, in containing one 

 additional atom of sulphur ; its formula is 10 Pr + So !*• 



Most of the chemical observations on protein apply equally 

 to albumen, and therefore without entering into any description 

 of the various chemical changes that occur upon the addition of 

 reagents, we shall simply notice the' physical appearances pre- 

 sented on the application of the ordinary tests. 



Albumen is precipitated from its fluid solutions by all the 

 ordinary acids, with the exception of acetic, tartaric, and phos- 

 phoric (tribasic) acids ; which not only do not precipitate 

 it, but check the ordinary precipitation induced by heat. It 

 is precipitated from its solution in these acids by ferrocya- 

 nide and fcrridcyanide of potassium, the former of which 

 yields a white, and the latter a yellow, precipitate. These pre- 

 cipitates are soluble in alkalies but not in acids. When 

 these two substances arc used as tests, theii' action may be im- 

 peded by the presence of free soda or its carbonate; the addition 



' See Apppiulix I, Note 7. 



