vin HEAT-COAGULATION 317 



coagulation of the albumin are induced at once when salts are added 

 to the heated solution. 



Starke and Erb give the following explanation : Albumins are 

 always denaturalised by heat, whatever the reaction and whether 

 salts are present or not, but the fate of the denaturalised albumin 

 depends on various factors. Denaturalised albumin is insoluble in 

 water and in neutral salt solutions soluble, however, in acids and in 

 alkalies. If therefore a feebly alkaline solution of albumin is heated, 

 there is formed at once a soluble salt consisting of the denaturalised 

 albumin and the metallic base ; while if an acid solution of albumin is 

 heated, there results analogously a soluble salt composed of the 

 denaturalised albumin and of the acid we added. Only if the reaction 

 is quite neutral does the denaturalised albumin, which in itself is 

 insoluble, become completely precipitated. 



The salts which denaturalised albumin forms with acids are called 

 acid -albumins ; those formed with bases are usually called alkali- 

 albuminates, but Schmiedeberg l and Maas 2 employ the term 

 'albuminic acids.' Paal 3 calls the denaturalised albumin which is 

 formed by the action of fixed alkalies protalbinic and lysalbinic acids. 

 Osborne 4 calls the denaturalised edestin edestan. The salts of 

 denaturalised albumin with hydrochloric, sulphuric, acetic acid, etc., 

 are very soluble in water, but they are precipitated by even traces of 

 salts. Alkali-albuminates are precipitated by larger amounts of 

 neutral salts ; of these alkali-albuminates the sodium-, potassium-, and 

 ammonium-salts are readily soluble, while the calcium-, barium-, or 

 strontium - salts are only slightly soluble. Therefore an alkali- 

 albuminate is precipitated by a large amount of sodium chloride 

 and by small amounts of a calcium salt. 5 



According to the view of Erb, 6 coagulation of serum-albumin takes 

 place in the following manner : An albumin solution containing no 

 traces of salt is completely precipitated by heat, and not a trace 

 remains in solution. The addition of a drop of dilute acid or 

 dilute alkali prevents the coagulation apparently completely, as 

 the solution remains clear on being heated ; but the acid solution is 

 completely precipitated if subsequently a trace of sodium chloride is 



1 0. Schmiedeberg, Arch. f. experiment. Path. u. Pharmakol. 39. 1 (1897). 



2 0. Maas, Zeitschr. /. physiol. Chem. 30. 61 (1900). 



3 C. Paal, Ber. d. deutsch. chem. Ges. 35. II. 2195 (1902). 



4 T. B. Osborue, Zeitschr. f. physiol. Chem. 33. 225 (1901). 



5 S. Ringer and H. Sainsbury. Journ. of Physiol. 12. 170 (1891) ; S. Ringer, ibid. 

 12. 378 (1891) ; also ibid. 13. 300 (1892) ; F. W. Tunnicliffe, Zentralbl. f. Physiol. 

 8. 387 (1894). 



6 W. Erb, Zeitschr. f. Biol. 41. 309 (1901). 



