THE CHEMICAL COMPOSITION OF THE BODY. 115 



which is quite insoluble in water. It is coagulated also by the prolonged 

 action of alcohol ; by strong mineral acids, especially by nitric acid, also 

 by tannic acid, or carbolic acid; by ethers the coaguluni is soluble in 

 caustic soda. 



It is precipitated without coagulation, i.e., forms insoluble compound 

 with the reagent, soluble on removal of the salt by dialysis, with either 

 mercuric chloride, lead acetate, copper sulphate or silver nitrate, the pre- 

 cipitate in each case being soluble in slight excess of the reagent. 



With strong nitric acid the albumin is precipitated at the point of 

 contact with the acid in the form of a fine white or yellow ring. 



Serum- Albumin is contained in blood-serum, lymph, serous and syno- 

 vial fluids, and in the tissues generally ; it may be prepared from serum, 

 after removal of paraglobulin by saturation with magnesium sulphate, by 

 a further saturation with sodium sulphate. It appears in the urine in the 

 condition known as albuminuria. 



It gives similar reactions to egg-albumin, but differs from it in not 

 being coagulated by ether. It also differs from egg-albumin in not being 

 easily precipitated by hydrochloric acid, and in the precipitate being easily 

 soluble in excess of that acid. Serum-albumin, either in the coagulated 

 or precipitated form, is more soluble in excess of strong acid than egg- 

 albumin. 



Albuminates. There are two principal substances belonging to this 

 class, a, Acid-Albumin; b, Alkali-Albumin. 



Acid- Albumin. Acid-albumin is made by adding small quantities 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 coagu- 

 lated native-albumin in strong acid, or by dissolving any of the globulins 

 in acids. Solid acid albuminate may be formed by adding strong acid 

 drop by drop to a strong solution of proteid matter (e.g., undiluted egg- 

 albumin) until solidification occurs. 



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

 tion a flocculent precipitate is produced (if it is then heated to 70 C. it 

 will coagulate and cannot then be distinguished from any other form of 

 coagulated proteids). This maybe shown by adding 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 it- 

 self is coagulated by strong acids, e.g., nitric acid, and by strong alcohol; 

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



