240 Scientific Intelligence. 



function of the dissolved salt. Nerxst has now pointed out that 

 since the osmotic pressure is also a function of the molecular mass 

 of the dissolved substance, a relation must exist between this 

 molecular mass and the quantity of the solvent which will be 

 dissolved out of the solution by a second liquid. Now, theory 

 indicates that the relative decrease in solubility toward a second 

 liquid which a solvent undergoes, owing to the addition of some 

 foreign substance is represented by the ratio of the number of 

 molecules of the dissolved foreign substance to the number of 

 molecules of the solvent. Hence, if n foreign molecules be dis- 

 solved in 100 molecules of the solvent, and if a be the solubility 

 of the pure solvent and a' that of the solution, (a— a')/a'=n/100. 

 The correctness of this conclusion the author has proved experi- 

 mentally, using solutions of various substances in valeric acid 

 and in ether, the second liquid being water. If therefore, x grams 

 of a substance whose molecular mass is M, be dissolved in 100 

 gram-molecules of the solvent, w=a?/M; and we have a means of 

 determining the molecular mass of the dissolved substance simply 

 by ascertaining the solubility of its solution in some second sol- 

 vent. Xeenst also proposes a new use of the freezing point 

 apparatus for determining molecular mass. If a mixture of two 

 liquids, such as ether and water for example be cooled to a low 

 temperature, the water will begin to freeze; and this will take 

 place at a temperature below zero, depending on the amount of 

 ether dissolved. If now a third substance be dissolved in the 

 ether, this substance not being soluble in water, it is evident that 

 the solubility of the ether in the water will be lessened and 

 the freezing point of the aqueous solution will be raised. So that 

 calling t Q the freezing point of a solution of ether alone in water, 

 and t the freezing point after the addition of m grams of a sub- 

 stance of molecular mass 31 to 100 grams of the ether, t/(t o —t) = 

 74 rn 100 M. For example, 2*04 grams benzene were dissolved 

 in 100 grams of ether and raised the freezing point 0*08° (cor- 

 rected). Calling E the "molecular depression" for ether alone 

 which is 3*06, and t! the corrected rise produced by the dissolved 

 substance, the above expression reduces to M=1£m/t'. Substitut- 

 ing the above numerical values, M=(3'06 X2-04)-^0-08 = 78'03, 

 the calculated molecular mass of benzene being 78. Using ethyl 

 acetate as the solvent, benzene gave values from 75 to 82, naph- 

 thalene from 123 to 143, xylene from 101 to 118, toluene from 

 93 to 100, chloroform from 113 to 137 and phenyl benzoate from 

 222 to 255. — Zeitschr. physikal. Chem., vi, 16; J. Chem. Soc, 

 lviii, 1368, Dec, 1890. ' G. f. b. 



3. On the Occurrence of free Fluorine in Iluorite. — Certain 

 varieties of flu or spar are known to emit a peculiar odor when 

 struck, which odor has been variously explained by different chem- 

 ists. Herrgott supposed the odor to be due to fluorine, Schaff- 

 hautl to hypochlorous acid, Schrotter to ozone, Schonbein to 

 antozone (given the name antozonite to a variety of fluorite which 

 emitted a very strong odor on fracture), Wyrouboff to a hydro- 



