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THE AMEBIC AN NATURALIST [Vol. XLIX 



of such a system are a pressure of water vapor equal 

 to 4 mm. of mercury and a temperature of .007° C. above 

 0° C— the freezing point at atmospheric pressure. 



Many applications of the phase rule to living matter 

 have been made. We will cite but one. The globulins— 

 typical proteins found in the blood of animals — are in- 

 soluble in distilled water, but are soluble in dilute solu- 

 tions of the inorganic salts, such as sodium chloride. The 

 globulin may exist in a system of water, sodium chloride 

 and globulin, as globulin in solution or as precipitated 

 globulin. The globulin is the only component existing 

 in more than one phase under the conditions of the ex- 

 periment. 30 * 1 Addition of water to the system to such a 

 degree that the concentration of the inorganic salts falls 

 below a certain minimum leads to a precipitation of part 

 of the globulin in solution. The removal of the mineral 

 salts, keeping the volume of the solution constant, will 

 also lead to precipitation wholly or in part, of the globulin 

 in solution. But whether water be added or salt removed, 

 the essential condition which undergoes changes is the 

 concentration of the salt.* Pressure does not enter in as 

 one of the conditions of the system. And if the tem- 

 perature of the system be raised above a certain point, 

 depending upon the globulin present in the system, the 

 globulin will be precipitated. In this system, the number 

 of components is one (globulin) and the number of phases 

 is also one, dissolved globulin. We have, therefore, a 

 system of n components with n phases, and two of the 

 conditions may vary, within certain limits, at the same 

 time, viz., the concentration of the sodium chloride and 

 the temperature. In the terminology of the quotation 

 above, P = l, C = l and F = 1 + 2 — 1, or 2. This is 

 also expressed by saying that the system is divariant. 

 This system is of interest because of the fact that it also 

 illustrates the phenomena of maximum points. 



