May 2, 1913] 



SCIENCE 



689 



The formula given in a previous publication for 

 the E.M.F. of liquid amalgam concentration cells 

 was integrated exactly and applied to those amal- 

 gams which have thus far been investigated with 

 sufficient accuracy, with the following results: 



1. The results of E.M.F. and vapor pressure 

 measurements with zine amalgams are shown to 

 be in very good agreement. In the light of the 

 vapor-pressure law this is shown to indicate that 

 in these amalgams the zinc exists uncombined 

 with the mercury but associated according to the 

 equation 



2Zn = Zn, + 2,400 joules. 



The equilibrium constant of this reaction, and 

 accordingly the degree of association at different 

 dilutions, is given, and shown to be in excellent 

 agreement with the measurements of E.M.F. and 

 its temperature coefficient. 



2. With lead and tin amalgams the same for- 

 mula relating E.M.F. with constitution as was 

 deduced for zine is shown to apply, but with a 

 different constant corresponding to a much greater 

 degree of association. 



3. The measurements on thallium amalgams are 

 shown to correspond to the formula derived for 

 the cases where combination exists between the 

 solute and the mercury. The compound indicated 

 in this case is TlHg„, which gives evidence of 

 breaking up into some simpler compound, prob- 

 ably TlHgj in the more concentrated amalgams. 



4. Indium amalgams, on applying the same for- 

 mula, seem to contain InHg^, breaking down into 

 some simpler compound in the more concentrated 



5. Cadmium amalgams seem to contain both 

 free Cd and the compound CdHg, in proportions 

 depending on the law of mass action. The E.M.F. 

 formula is derived for this case and shown to give 

 the observed values of E.M.F. very closely. The 

 per cent, of the cadmium as CdHg is calculated. 

 In the most dilute amalgams two thirds of the 

 cadmium is present as CdHg. 



The validity of the formula is discussed and its 

 value is pointed out in determining the constitu- 

 tion of metallic solutions and as a means of in- 

 vestigating the present unknown factors influ- 

 encing the vapor pressure of solutions. 



Albeet D. Brokaw : The Precipitation of Gold iy 



Manganous Salts. 



Ordinary solutions of gold chloride are rather 

 strongly acid, and from such solutions manganous 

 salts do not precipitate gold even when high con- 



centrations are used and the solutions kept boiling 

 for some little time. When the acidity is suffi- 

 ciently reduced manganese dioxide and gold are 

 precipitated simultaneously, probably according to 

 some such equation as follows: 



SMnClj + 2AuCla + GH^O -> 



3MnO, -t- 2Au + 12HC1. 



A suggested explanation is that minute amounts 

 of MnCli are formed and this substance hydrolyzes 

 when the acidity falls below a certain concentra- 

 tion, giving a precipitation of hydrated mangan- 

 ese dioxide. In more acid solution the acidity 

 suppresses hydrolysis and no reaction takes place. 



Hans Mannhabdt: Tetravalent (.?) Nitrogen and 



Di-Valent (?) Chlorine. 

 H. V. Tartar: Oji the Reaction of SvXphur with 



FotassiiLm Sydroxid in Aqueous Solutions. 



Methods have been worked out in connection 

 with some investigations on the lime-sulphur 

 spray which enable one to ascertain the primary 

 reaction taking place between sulphur and any of 

 the hydroxids of the alkali metals in aqueous 

 solution. Experiments were tried using sulphur 

 and potassium hydroxid in different amounts and 

 in solutions of varying concentration. The results 

 show that the primary reaction of sulphur with 

 potassium hydroxide in aqueous solution is as 

 represented by the following equation: 



6K0H + 8S = 2K,S3K,S,03lL,0. 



Fritz Friedrichs: Binary Systems. I. Hydra- 

 zine, Ammonia. 



In this research, which constitutes the first 

 chapter of an extended investigation of the na- 

 ture of supplementary valence, the relation of 

 ammonia to hydrazine, the next member of the 

 hydro-nitrogen series, has been studied. 



A dilatometric study of the purest hydrazine 

 (shown by analysis to contain 100 per cent. 

 N2H4 and subsequently distilled twice in vacuo 

 over pure barium oxide directly into the dilatom- 

 eter) showed a unary melting point of + 3.3°, 

 indicating a very high degree of purity. This 

 pure hydrazine forms no compounds with anhy- 

 drous ammonia. The presence of the slightest 

 trace of water, however, leads to the formation o£ 

 mixed crystals. The complete pressure, tempera- 

 ture, concentration diagram of this system was in- 

 vestigated. The three-phase surface shows a pres- 

 sure maximum of 630 mm. at — 19°, the solubility 

 line a euteetic at — 81° and a concentration of 

 85 per cent. NH3. 



