350 PHYSICAL PROPERTIES 



This phenomenon was investigated more fully by Schulz and 

 Zsigmondy (10), who define the number of milligrams of a colloid 

 which is just insufficient to prevent 10 cc. of a colloidal gold solu- 

 tion from showing a change in color after the addition of 1 cc. 

 of 10 per cent NaCl solutions as the "gold-number" of the colloid. 

 It appears to be highly characteristic for certain proteins. The 

 following are the values determined by Schulz and Zsigmondy for 

 the various proteins contained in or derived from egg-white: 



Globulin 0.02-0.05 



Ovomucoid 0.04-0.08 



Crystallized egg-albumin 2 . 00-8 . 00 



Other (con-) albumin 0.03-0.05 



Alkali-albuminate 0.006-0.04 



The great difference between the crystalline albumin "gold- 

 number" and that of the other proteins in egg-white made it 

 possible to recognize the presence of very small quantities of 

 colloidal contamination in the egg-albumin. Schulz and Zsig- 

 mondy were able to show by this method that egg-albumin must 

 be recrystallized from three to six times to remove appreciable 

 quantities of such contaminations. 



The determination of the "gold-number" of cerebro-spinal 

 fluid has been found to be of very great value in the differential 

 diagnosis of the various forms of syphilitic sequelae, the modifi- 

 cations observed being attributable to the marked increase in 

 globulin-content which accompanies and characterizes certain of 

 these conditions. 



LITERATURE CITED 



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483. 



(2) Arrhenius, S., Zeit. f. physik. Chem., 1 (1887), p. 285. 



(3) Arrhenius, S., "Immunochemistry," New York (1907). 



(4) Barcroft, J., and Hill, A. V , Journ. of Physiol., 39 (1910), p. 411. 



(5) Bayliss, W. M., Proc. Roy. Soc, London, 81 (1901), p. 269. 



(6) Bechold, H., and Ziegler, J., Zeit. f. physik. Chem., 56 (1906), p. 105. 



(7) Benedicenti, A., Biochem. Zeit., 63 (1914), p. 276. 



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(9) Berczeller, L., Biochem. Zeit., 53 (1913), pp. 215 and 232. 



(10) Berthellot, M. P. E., "Essai de Statique Chemique," Paris (1803). 



(11) Berthold, G., "Studien ueber Protoplasmamechanik," Leipzig (1886). 



(12) Bottazzi, F., Arch. Ital. de Biol., 29 (1898), p. 401. 



