16 CHEMISTRY OF THE PROTEIDS CHAP, i 



taurocholic, and chondro-sulphuric acids l also precipitate, provided the 

 reaction be acid. 



The precipitation of albumins, and partly also that of albumoses, 

 by means of strong mineral acids such as hydrochloric, nitric, 

 sulphuric, and phosphoric acids, differs somewhat from the precipitation 

 described above. The reaction with nitric acid is so sensitive that it 

 is used clinically for detecting the presence of albumin in urine. 

 True albumins are insoluble in an excess of acid and when heated, but 

 not so the albumoses. With the latter the precipitate disappears on 

 heating and reappears on cooling. On heating we see in addition to 

 the precipitation also the xanthoproteic-reaction. 



Microscopic Investigations 



The behaviour of albuminous substances, under different physical 

 and chemical conditions, is fully discussed in the author's Physiological 

 Histology? whose chief result, as far as structure is concerned, may be 

 summed up thus : Electrolytes do, while non-electrolytes, such as 

 formaldehyde and osmium tetroxide, do not, produce artefacts in 

 ' fixing ' tissues. 



The ultra microscopical nature of albumins has been studied by 

 F. Raehlmann, 3 by Michaelis, 4 Pauli, 5 and Waymouth Reid. 6 



1 See under respective acids. 



2 Gustav Mann, Physiological Histology: Theory and Methods. Clarendon Press, 

 1902. 



3 F. Raehlmann, Berliner Idin. Wichensch. 1904, 'p. 186. 



4 L. Michaelis, Virckwfs Arch. 179. 195 (1905). 

 " 5 W. Pauli, Hofmeisters Btitrage, 6. 258 (1905). 



* 6 E. Waymouth Reid, Jowrn. of Physiol. 33. 12 (1905). 



