96 



SCIENCE 



[N. S. Vol. XLII. No. 1072 



Paul M. Giesy and James E. Withrow: The 

 Electrolytic Preparation of Solid Alkali Amal- 

 garnis in Quantity. 



Kerp, by his method, obtained 200 gr. of solid 

 potassium amalgam in 4 to 5 hrs. This method 

 has been modified so as to yield 490 gr. in J hr. 

 As previously found, Shepherd's method did not 

 give pure amalgams. Smith and Bennett, by their 

 method, using 3 amp. current, obtained about 

 180 gr. solid sodium amalgam. By using 20 amp. 

 current, and cooling the cell by an ice-water bath, 

 680 gr. were obtained in 2i hrs. It is not neces- 

 sary to cool the cell in the ease of potassium 

 amalgam. After eleetrolyzing 50 min. with 

 1,000 gr. mercury and 20 amp. current, 1,015 gr. 

 of solid potassium amalgam were obtained by 

 chiUing. 



O. L. Barnebey: 'Permanganate Determination of 

 Iron in the Presence of Fluorides. The Analysis 

 of Silicates and Carionates for their Ferrous 

 Iron Content. 



In a systematic study of the effect of various 

 reagents toward increasing the accuracy of ti- 

 trating ferrous iron in the presence of fluorides, 

 boric acid was found to give the best results. 

 Boric acid when added to the ferrous solution pre- 

 ceding titration converts the hydrofluoric acid to 

 metafluoboric acid, HBF,, which does not inter- 

 fere with the permanganate reaction. This use of 

 boric acid is applied in the analysis of silicate and 

 carbonate rocks for their ferrous iron content. 



0. L. Barnebey: The Permanganate and lodi- 

 metric Titration of Iodide in the Presence of 

 Bromide and Chloride. 



The Pean de St. Gilles permanganate method of 

 titrating iodide to iodate has been modified by 

 adding manganous sulfate with the ferrous sulfate 

 in removing the excess of permanganate. This 

 prevents the liberation of bromine or chlorine at 

 this stage of the analysis as well as later when 

 titrating the excess of ferrous sulfate with the 

 permanganate. After the completion of the per- 

 manganate titration the iodate formed may be de- 

 termined by adding phosphoric acid and potassium 

 iodide and titrating the liberated iodine with thio- 

 sulfate. 



Hal Walters Moselet: The Phenomenon of 

 Passivity in Connection with Ferrous Alloys of 

 Different Composition and Structure. 

 The author has shown that samples of iron and 



steel of very different composition and structure 



can be made passive with a definite current den- 

 sity when the samples were made the anode in an 

 electrolytic cell. The nature and concentration of 

 the electrolyte are also factors influencing the es- 

 tablishment of the passive state. The current 

 density required is not related in any simple way 

 to the composition or structure of the samples. 



The results confirm the view that the phenom- 

 enon is perfectly general for all classes of irons 

 and steels, and show that passivifying agents as 

 inhibitors of corrosion have a very wide applica- 

 bility. 



William C. Moore: The Thermo-electric Proper- 

 ties of Carbon. 



Preliminary experiments with various combina- 

 tions of arc carbons as thermo couples showed that 

 each particular combination had individual thermo- 

 electric characteristics. 



More elaborate measurements were then made 

 with various carbon copper couples. The burning 

 of such couples at high temperatures was so seri- 

 ous that the simple carbon copper couple was 

 modified by enclosing the arc carbon rod vidthin 

 a copper tube, the combination serving as a couple, 

 the tube being partially exhausted by a water 

 pump. 



With several of the carbon-carbon couples and 

 some of the carbon-copper couples, a point or a 

 region of maximum electromotive force was found. 

 With one carbon-copper couple this region ex- 

 ceeded from 741° C. to 816° C. ; with another car- 

 bon-copper couple, this region exceeded from 514° 

 C. to 565° C. These carbons were of different 

 composition and had different manufacturing his- 

 tories. The temperature coefficient of the electro- 

 motive force of these couples was very irregular 

 before reaching the region of maximum electromo- 

 tive force; after passing through this region this 

 coeflScient became more regular, and the slope of 

 the de/dT — T curve changed. The carbon was 

 negative at the cold end, but in one case became 

 positive at a high temperature. The carbon used 

 in a different carbon copper couple was positive 

 throughout the experiment, an E.M.F. of 2.18 

 millivolts being reached when the furnace tem- 

 perature was 878° C. In this case the electromo- 

 tive force did not pass through a maximum. 



The electromotive force of the one carbon-car- 

 bon couple reached a value of 14.59 millivolts at 

 a furnace temperature of 707° and a cold junc- 

 tion temperature of 55.5°. 



In general, this is higher than that reached by 



