December 22, 1922] 



SCIENCE 



725 



especially those wliieli lie below hydrogen in the 

 electromotive force series. 



Seliavior of aqueous potassium permanganate 

 in the presence of potassium hydroxide : William 

 Lbkch and J. E. Day. The rate of decomposi- 

 tion of an aqueous solution of potassium perman- 

 ganate (free from reducing substance) in the 

 presence of varied amounts of potassium hy- 

 droxide (free from reducing substances) was ob- 

 served at the temperatures 75 land 105° Centi- 

 grade (approximately) For a concentration of 

 KOH at and below 0.7 M no change in oxidiziug 

 potential occurred at 73° in 182 hours. Increas- 

 ing temperature and alkalinity resulted in an in- 

 crease in the per cent, of KMn04 converted to 

 K2Mn04. At 105° Centigrade and a causticity of 

 11.7 M the percentage change was 90.3. The rate 

 oi change curves are log curves. 



Some properties of arsenic trioxide in aqueous 

 solution: Ernest Anderson and R. G. Story. 

 The density and refractive index curves of AS2O3 

 in aqueous solution were found to be straight 

 lines. The equation for such a curve is: 

 W = A -\- BX. The constants A and B for botJi 

 curves were accurately determined at 25° C. The 

 weight of AS2O3 eajlculaited from either density 

 or refractive index by the constants A and B 

 agree exactly with analytical determinations. The 

 solubility curve, degree of hydraifnou and hydro- 

 gen ion concentration were also determined for 

 AS2O3 in aqueous solutions. 



Preparation of antimony-free arsenious tri- 

 oxide: C. W. FouLK, P. G. HoRTON and G. M. 

 McClure. Arseuions trichloride is first prepared 

 either bj' heating the oxide with concentrated hy- 

 drochloric aoid and distilling or by adding sul- 

 furic acid to the hydrochloric acid solution and 

 drawing off the layer of trichloride. The sepai'a- 

 tion from antimony can be effected by several 

 distillations of the arsenious trichloride or better 

 and easier by shaking the trichloride two or 

 three times on a separatory funnel with a little 

 less than its own volume of concentrated hydro- 

 chloric acid. The antimony goes into the water- 

 acid phase. 



The determination of lead in lead amalgam: 

 M. G. Mellon. Lead in lead amalgam may be 

 displaced by copper from an aqueous solution of 

 copper nitrate vat\i the formation of copper amal- 

 gam and lead nitrate. The lead may then be 

 precipitated and weighed as the chromate. Data 

 are given to show the accuracy of the method 

 and the effect of time, temperature and concen- 

 tration of copper nitrate upon the displacement 



reaction. The mercury is not dissolved in the de- 

 termination, and it may be purified for further 

 use. 



The volumetric determination of phosphorus: 

 William A. Turner. Experiments undertaken 

 using the Pemberton or Kilgore volumetric meth- 

 od for phosphorus show a positive error of ap- 

 proximately S per cent, when compared with 

 results obtained by the gravimetric method. It is 

 shown that the factor for the phosphorus equiva- 

 lent of the aUiali solution as given in the official 

 methods of the A. O. A. C. and in many text- 

 books is derived from an incorrect reaction. The 

 precipitate of ammonium pho^phomolybdate as 

 ordinarily produced contains aoid not removed by 

 washing with a neutral salt solution. The pre- 

 cipitate, therefore, is not (NH4)3P04 . I2M0O3, 

 as commonly assumed, but (NH4)3P04 . I2M0O3 

 -\- 2 mols. HNO3 or an equivalent amount of some 

 other acid. Such a precipitate requires a larger 

 proportion of alkali. The correct reaction is, 

 2[(NH4)3P04.12Mo03.2HN03] + 50NaOH = 

 2(NH4)2HP04 + (NH4)2Mo04 + 23Na2Mo04 + 

 4NaNo3 -U 26H2O. A factor calculated on this 

 basis calls for an S per cent, reduction in the phos- 

 pihoTus equivalent of the alkali solution. Such a 

 factor gives results which agree very closely with 

 the gravimetric method. 



Note on apparatus for preparation of conduc- 

 tivity waters: C. W. FouLK and A. P. Bawden. 

 The device is an accessory for conductivity water 

 sitills because its use eliminates corks or rubber 

 stoppers for connecting glass flasks with con- 

 densers. Briefly, it consists of a circular tin 

 block on one end of which an annular depression 

 is turned to engage the mouth of the flask to be 

 used. Gaskets of tin-foil can be employed if 

 neoessajy. The block is held in place by means 

 of springs stretched between it and a brass collar 

 around the neck of the flask. The inner tube of 

 tlie condenser passes through a hole in this block, 

 the connection being made hj solderiug with tin. 



DeterminatioH of the specific gravities of mini- 

 mal amounts of materials hy the immisciile bal- 

 ance: William G. Exton. I<t is often necessary 

 (blood and other body fluids, scums, dust, etc.) 

 or expedient (viscosity, expense of materials, etc.) 

 to determine the specific gravity of minimal 

 amounts of liquids or solids, and this may be 

 done rapidly and conveniently with the immiscible 

 balance. The material rto be tested is suspended 

 in equilibrium in a mixture of two solutions 

 (light and heavy) which are miscible with eax;h 

 other but not with the sample, i. e., petroleum 



