﻿Chemistry and Physics. 477 



picrotoxine and picrotoxide hydrate, santonin and santonid. 

 Raoult's method was strictly followed. The quotient of the de- 

 pression of the freezing point in degrees by the concentration of the 

 solution, i. e., the weight of substance in 100 c.c. of it, gives the de- 

 pression coefficient, or the depression given by one gram of the sub- 

 stance in 100 c.c. This, multiplied by the molecular weight, gives 

 the molecular depression. Thus, for aldehyde C 2 H 4 in water the 

 depression-coefficient for various strengths of solution, was 0*4107, 

 0*4274, 4279 and 0*4369 ; the corresponding molecular depres- 

 sions being 18*07, 18*81, 18*83 and 19*22. For paraldehyde 

 (C 2 H 4 0) 3 , the depression-coefficient was 0*1458, 0*1513, and the 

 molecular depression 19*24 and 19*97; practically the same. 

 Cyanamide CN 2 H 2 has a molecular depression of 16*28, dicyan- 

 amide (CN" 2 H 2 ) 2 of 15*54. Acetonitrile CH 3 . ON afforded a molecu- 

 lar depression of 17*78, 17*28, and 18*61 in three experiments; but 

 cyanmethin (CH 3 . CN) 3 varied its depression-coefficient from 0*0786 

 to 0*0461 according to the concentration of the solution ; giving a 

 molecular depression varying from 5*67 to 9*67. This would sug- 

 gest a molecule two or three times as large, either (CH 3 . CN) 6 or 

 (CH 3 .CN) 9 ; values not in accordance with the vapor density or 

 chemical behavior of this substance. Lapachoic acid C 16 H 14 3 in 

 benzene gave a molecular depression of 46*37 ; and lapachon, with 

 the same formula, one of 43*10. Picrotoxine C 12 H 14 5 , in acetic 

 acid, gave 43*15, and 43*22; while picrotoxide hydrate C 15 H 18 7 

 gave 44*98 and 40*98 in two experiments. In general the authors 

 consider Raoult's law to be exact, and regard- it of great value in 

 fixing molecular weights. Their experiments are to be continued. 

 —Ber. Berl. Chem. Ges., xix, 2527-2530, Oct. 1886. G. f. b. 



3. On the Magnetic Rotation of mixtures of the tatty Acids, 

 of Alcohol and of Sulphuric Acid, with Water. — Perktn has 

 continued his researches upon the relation between the chemical 

 constitution of substances and their power of rotating the plane 

 of polarization when under magnetic influence,* and has now 

 given the results of his examination of the rotation produced in 

 mixtures of water with the fatty acids, with alcohol and with 

 sulphuric acid. He calls the specific rotation of a substance the 

 ratio of its observed rotation to that of water under the same 

 conditions. By multiplying the specific rotation thus obtained 

 by the ratio of the molecular weights of the substance and of 

 water, and then dividing by the density of the substance, the 

 molecular rotation of the given substance is ascertained. In a 

 previous memoir, he had shown that the molecular rotation of 

 water, assumed as unity, is not the same as the sum of the values 

 of oxygen and two of hydrogen as deduced from the molecular 

 rotation of other compounds. Thus hydrogen is found to be 

 0*254, while oxygen in hydroxyl varies from 0*194 in ordinary 

 alcohols to 0*137 in monobasic acids, and is 0*261 in carbonyl. 

 Taking the lowest numbers, H 2 -f- = 0*645, and the highest, it 

 is 0*769, instead of one. This difference between the molecular 



* See J. Chem. Soc., xlv, 421-580, Sept., 1884. 

 Am. Jour. Sci. — Third Series, Yol. XXXII, No. 192. — December, 1886. 

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