590 PHAGOCYTOSIS OF SOLID PARTICLES. IQ 



energy of a quartz-serum surface, other things being equal. It is 

 interesting that this is exactly the condition which should also cause 

 more rapid clumping of the carbon than the quartz, since clumping 

 involves a decrease of surface. It has already been mentioned that 

 this difference in stability is the one outstanding distinction between 

 quartz and carbon.^ 



According to Bredig (14) a low surface tension between a particle 

 and a liquid should correspond to a high electric charge, thus recon- 

 ciling electrical and surface tension theories of coagulation. If this 

 theory is correct quartz should carry a higher charge than carbon, 

 and the available evidence in the literature indicates that this is so. 

 Thus, Whitney and Blake (15) measured the charge on quartz parti- 

 cles by kataphoresis and found a rather high negative charge of 

 0.042 volts. Rona and Michaelis (16) found that H and OH ions 

 were equally adsorbed by carbon, and concluded, in consequence, 

 that carbon must carry no electric charge. This opinion was, more- 

 over, corroborated by a statement of Freundlich's (which they quote 

 in a footnote) to the effect that this lack of a charge on carbon accounts 

 for difficulty which he had experienced in trying to measure the kata- 

 phoresis of carbon. Rona and Gyorgy (17) were led to the same 

 postulate concerning carbon by measurements of the effect of non- 

 electrolytes on the speed of settling. 



Some attempts were made to confirm this difference between the 

 electric charges on quartz and carbon qualitatively by measuring the 

 stability of the suspensions in various concentrations of sodium 

 hydroxide and hydrochloric acid. Uniform suspensions, 2 to 3 

 microns in diameter, of quartz and carbon were used, and the degree 

 of coagulation in the different solutions was determined by counts 

 of the total number of particles, aggregate and single, in the case of 

 carbon, and of the number of clumps in the case of quartz. The 

 coagulation of quartz was so slight even in the most effective con- 

 centration of hydrochloric acid that there was scarcely a measurable 

 decrease in the total number of particles. Both suspensions showed 

 greatest stability in neutral and alkaline solutions and both showed an 



■* In agreement with this hypothesis is the fact that manganese dioxide is 

 ingested by leucocytes with extraordinary rapidity compared to manganese sili- 

 cate, and is also much less stable in suspension. 



