420 ALBUMINOUS COMPOUNDS. 



lation may be produced at a temperature between 20 C. and 

 30 C. (Hoppe-Seyler). 



f Coagidation z.s- not due to heat alone, but to the presence of 

 }\'dfrr. Take some perfectly dry albumin, put it in a test-tube, 

 cover the mouth of the tube and plunge its lower end into 

 boiling water. Keep it there sufficiently long to be certain that 

 the albumin has been heated to 100 C. Take it out, let it 

 cool, and then add water to the albumin. It will be found solu- 

 ble. Plunge the tube a second time into the boiling water, and 

 the solution will be coagulated. 



** 9. Precipitation of Albuminous Bodies. Though 

 the action of the following reagents may be conveniently tried 

 with a solution of egg albumin, their power of precipitating 

 albumin is not limited to that obtained from eggs, but extends 

 equally to all other albuminous bodies. 



Take a solution of albumin in water, put some of it into ten 

 tcst-lul' following reagents. They all precipitate 



albumin. 



1. Concentrated nitric acid. 

 V 2. Concentrated hydrochloric acid. 

 * 3. Concentrated sulphuric acid. 



Acetic acid, or a little hydrochloric acid, and afterwards 

 a solution of potassium ferrocyanide. 



5. Acetic acid and a considerable quantity of a concentrated 

 solution of sodium sulphate. [Other neutral salts of the alkalis 

 or alkaline earths as well as gum arable or dextrin have a simi- 

 lar action to sodium sulphate.] 

 v. ('). P>:isie lead acetate. 

 M 7. Mercuric chloride. 

 < 8. Tannic acid. 



9. Powdered potassium carbonate thrown into the solution 

 till it is almost saturated. 

 10. Alcohol. 



* 10. Detection of Albumin. The three tests ordina- 

 rily used to deteel the presence of albumin in a fluid are 



1st. Its precipitation when boiled and acidulated with nitric 

 acid. 



iM. Its precipitation by acetic acid and ferrocyanide of 

 potassium. 



M. Its precipitation when boiled with acetic acid and a strong 

 solution of neutral salt. 



The student should first try these tests with a solution 

 known to contain albumin, so as to become familiar with them, 

 and afterwards with a solution which may or may not contain 

 it. 



1. Put some of the fluid in a test-tube and heat it over a 

 spirit-lamp or Uunsen's burner till it boils. Add a drop or 

 two of nitric acid so as to give it a most distinctly acid reac- 



