736 APPENDIX. 



ent temperatures, viz., a. at 73 C., ft. at 77 C., and y. at 85 C., as 

 demonstrated by Halliburton, as well as its other properties, are men- 

 tioned at p. 79. 



CLASS II. DERIVED- ALBUMINS. 



(A) Acid-Albumin. Acid-albumin is made by adding small quanti- 

 ties of dilute acid (of which the best is hydrochloric, .4 per cent to 1 per 

 cent), to either egg- or serum-albumin diluted with five to ten times its 

 bulk of water, and keeping the solution at a temperature not higher than 

 50 C. for not less than half an hour. 



It may also be made by dissolving coagulated native-albumin in 

 strong acid, or by dissolving any of the globulins in acids. 



It is not coagulated on heating, but on exactly neutralizing the solu- 

 tion, a flocculent precipitate is produced. This may be shown by ad- 

 ding to the acid-albumin solution a little aqueous solution of litmus, 

 and then adding, drop by drop, a weak solution of caustic potash from 

 a burette, until the red color disappears. The precipitate is the derived 

 albumin. It is soluble in dilute acid, dilute alkalies, and dilute solutions 

 of alkaline carbonates. 



The solution of acid-albumin gives the proteid tests. The substance 

 itself is coagulated by strong acids, e. g., nitric acid, and by strong alco- 

 hol; it is insoluble in distilled water, and in neutral saline solutions; it is 

 precipitated from its solutions by saturation with sodium chloride. On 

 boiling in lime-water it is partially coagulated, and a further precipita- 

 tion takes place on addition to the boiled solution of calcium chloride, 

 magnesium sulphate, or sodium chloride. 



(B) Alkali- Albumin. If solutions of native-albumin, or coagulated 

 or other proteid, be treated with dilute or strong fixed alkali, alkali-albu- 

 min is produced. Solid alkali-albumin may also be prepared by adding 

 caustic soda or potash, drop by drop, to undiluted egg-albumin, until 

 the whole forms a jelly. This jelly is soluble in dilute alkalies on boil- 

 ing. 



A solution of alkali-albumin gives the tests corresponding to those 

 of acid-albumin. It is not coagulated on heating. It is thrown down 

 on neutralizing its solution, except in the presence of alkaline phos- 

 phates, in which case the solution must be distinctly acid before a pre- 

 cipitate falls. 



To differentiate between Acid- and Alkali- Albumin, the following 

 method may be adopted. Alkali-albumin is not precipitated on exact neu- 

 tralization, if sodium phosphate has been previously added. Acid-albu- 

 min is precipitated on exact neutralization, whether or not sodium phos- 

 phate has been previously added. 



(c) Casein. Casein is the chief proteid of milk, from which it 

 may be prepared by the following process: The milk should be diluted 



