Decembee 9, 1921] 



SCIENCE 



583 



pointed out, early in the nineteentli century, tliat 

 ethyl chloride prepared by the method of Dumas 

 and Peligot contains ethyl ether as an impurity. 

 In a paper presented at the last meeting of this 

 Society (see Science, 53, 582 (1921)), we showed 

 that methyl chloride prepared by the above method 

 (that is 'rom salt, sulfuric acid and methyl alco- 

 hol) could not readily be separated from methyl 

 ether which it contains as impurity, and that the 

 presence of methyl ether can be detected by addi- 

 tion of boron trifluoride, which forms the molecular 

 compound (CH3);0.BFs, boiling at 126° C, and re- 

 maining as a slightly volatile residue after evapora- 

 tion of the excess of either gaseous constituent. At 

 the present time, methyl chloride prepared by cWor- 

 ination of natural gas is available and a sample 

 was obtained through Eoessler and Hasslacher. 

 This sample appeared to contain methane, which 

 is somewhat soluble in liquid methyl chloride. A 

 large sample was collected and fractionally distilled 

 five times, after which it distilled at a uniform 

 pressure. Tested by addition, of boron trifluoride, 

 the product was completely volatile, showing that 

 the sample was free from methyl ether. The freez- 

 ing point curve obtained shows a sharp euteetic at 

 30 per cent, of methyl chloride, where the freezing 

 point was about 137 degrees below zero. There is 

 no indication of the formation of a compound be- 

 tween methyl chloride and boron trifluoride. 



The application, of a differential thermometer in 

 ehullioscopy : Alan W. C. Mbnzies and Sydney 

 L. Wright, Jr. The differential thermometer, per- 

 haps 12 cm. long, is extremely simple but of novel 

 type, consisting essentially of a stout glass U-tube 

 containing only water and its vapor, and measures 

 the difference in temperature between the solution 

 and the pure solvent. Both limbs of the ther- 

 mometer are located in the vapor phase; one of 

 them is laved continually with the solution by 

 means of a Cottrell pump, while the other is laved 

 only by condensed solvent. The apparatus uses 

 neither corks nor stopcocks, is rather insensitive to 

 draughts and to changes in heating, and is un- 

 affected by barometric fluctuation. Eesults are con- 

 sistent to one half of one per cent. 



The decolorizing action of honehlacTc : Claude 

 H. Hall, Jr. The author has repeated and con- 

 firmed the work of Patterson. By extraction of 

 hydrochloric acid washed boneblack with sulfuric 

 acid an extremely active decolorizing agent may be 

 prepared. By precipitating this compound on wood 

 charcoal, or other porous substances, a material 

 identical in chemical action with boneblack is ob- 



tained. This is the final link in the chain of evi- 

 dence proving that the decolorizing action of bone- 

 black is due to certain nitrogeneous compounds, the 

 empirical formula and some of the properties of 

 which are described in the previous reference. 



Effect of electrostatic potential on the activity 

 of a catalytic surface: A. S. Richardson. 



The selenides of ammonium: C. E. McCroskt 

 and a. J. King. Pure dry NHj and H,Se were 

 admitted to a special weighing tube, free from 

 oxygen. White crystals form when H.Se is in ex- 

 cess — analyzing from 76 per cent.i to 80 per cent. 

 Se, corresponding closely to NH,HSe. This salt 

 dissociates without melting at 100° to 120°. When 

 NH3 is in excess and the temperature of the tube 

 is kept at from 20° to 30°, a liquid forms, prac- 

 tically colorless. (The heat of formation of 

 NHjHSe is great enough to prevent the formation 

 of the liquid unless the tube is cooled to room 

 temperature.) The analysis of this liquid shows 

 Se 68 per cent, agreeing with the theoretical for 

 (NH4)„Se. It freezes at approximately 10° and 

 decomposes at 30° to 40° leaving the white crystals 

 of the hydroselenide. Bineau (1838) claims that 

 (NH4)jSe is a white solid, also that NHjHSe is a 

 white solid. Lehner and Smith (1898) prepared a 

 dark-colored crystalline solid from water solution, 

 which corresponded to (NHi),Se. Further definite 

 data are lacking in the literature. 



The correlation of compound formation and 

 iomzation in solutions : James Kendall and Paul 

 M. Gross. The complete specific conductivity-com- 

 position curves for 14 systems of the types: acid- 

 ester, acid-ketone, acid-acid and acid-base have 

 been determined. The conductivities of mixtures of 

 the above types are, in general, considerably in ex- 

 cess of those of the pure components, and increase 

 rmiformly with increasing diversity in chemical 

 character of these components. The- results ob- 

 tained have been correlated vrith those derived 

 from freezing-point measurements upon similar sys- 

 tems, and the validity of the fundamental connec- 

 tion between compound formation and ionization in 

 solutions, postulated in previous articles, has been 

 confirmed. 



The prediction of solubility in polar solutions: 

 James Kendall, Arthur W. Davidson and 

 Howard Adler. The influence of compound forma- 

 tion between solvent and solute on the degree of 



1 Errors in the method, found lat«r, in all prob- 

 ability account for the low values. These errors 

 were overcome in later determinations. 



