426 



SCIENCE 



[Vol. LVI, No. 1450 



peratures below 200° F. is substautially inde- 

 pendent of the hydrogen ion concentration and is 

 directly proportional to the oxygen concentration. 

 Specific rates of corrosion are then calculated in 

 terms of the weight of iron corroded per unit 

 area, per unit time, per unit concentration of 

 oxygen. Units are suggested for the specific 

 rates of corrosion, and formulaB given for calcu- 

 lating these rates from data on (a) loss in weight 

 of test pieces and (6) drop in oxygen content of 

 water. By thus correcting for the effeat of oxy- 

 gen concentration, etc., it is possible to compare 

 rates of corrosion under different conditions and 

 determine the precise effect of velocity, tempera- 

 ture, etc. It appears that the specific rates of 

 coi'rosion depend more on velocity than on any 

 other single factor and that the composition of 

 the metal and the hydrogen ion concentration are 

 generally unimportant in under-water corrosion. 



A new method of measuring corrosion tinder 

 water. Investigation of effect of velocity: F. N. 

 Spellek and V. V. Kendall. Subaqueous cor- 

 rosion is nearly proportionate to the concentration 

 of oxygen dissolved in water, which fact is used 

 for measuring the amount of corrosion in the ex- 

 periments described. Water is passed through a 

 certain length of %-inch, i^-inch and %-inch 

 commercial steel pipe, uneoated, and the corrosion 

 is measured by the difference in coneentratior of 

 dissolved oxygen. Time of contact was held con- 

 stant by varying the length of pipe. Velocities 

 from Vio foot per second to 8 feet per second 

 \Yerc obtained. Corrosion-velocity curves are given 

 for each size pipe, for temperatures ranging from 

 60° to 170° F. Corrosion is found to increase 

 with velocity in all cases, but at a decreasing 

 rate. Eate of corrosion accelerates rapidly with 

 rise in temperature over 90°, velocity and all 

 other conditions being constant. This method of 

 measuring corrosion is applicable to the investi- 

 gation of the influence of other factors on sub- 

 aqueous corrosion, such as composition of the 

 metal, character of the water, etc. 



The action of sodium silicate v:hen used mi 

 soaps: A. S. Richaudson. The possible advan- 

 tages of sodium silicate in soap have been studied 

 under the following headings: Water softening 

 action; detergent action without admixture of 

 soap; and effect on emulsification power of soap. 

 The soap-sparing effect of sodium silicate varies 

 with the conditions of its use, being most pro- 

 nounced at high temperature and in hard water 

 high in magnesium salts, under which conditions 

 the amount of soap conserved may be more than 



the chemical equivalent of the sodium silicate 

 used. Sodium silicate has probably no detergent 

 action when used without soap, except in so far as 

 free fatty acid is present in the wash. However, 

 sodium silicate increases the emulsifying power 

 of soap solutions, as shown by a decrease of the 

 surface tension of the soap solution toward a 

 mineral oil. 



Counter-current digestion of wood hy the soda 

 process: K. T. Haslam and W. P. Etan. From 

 a consideration of the law of mass action, the 

 digestion of wood by the soda process seems to 

 offer a field for the application of the counter- 

 current principle. Ungerer, an Austrian chemist, 

 patented the equivalent of such a process in 

 1872, but no record is found of its commercial 

 application. Eecent work has shown that by 

 passing the soda solution in counter-current direc- 

 tion to the wood chips the time required for 

 digestion can be decreased by one third to one 

 half that of the usual batch process, that the 

 yields on small scale equipments are from 2 to 10 

 per cent, lower, .that a better bleaching pulp is 

 obtained and that the alpha (resistant) cellulose 

 content of the pulp is materially increased. 



Factors influencing the efficiency of alTcali- 

 chlorine cells: W. P. Eyan, C. T. Hasding and 

 E. P. KusSELL. A study of the effect of efSuent 

 flow vs. current efficiency at four current densities 

 shows that the efficiency increases rapidly with 

 increased flow, approaching 100 per cent, asym- 

 photically. A plot of current density vs. effiuent 

 flow at the guaranteed (92 per cent.) efficiency is 

 of especial interest to plants forced to run at 

 varying current densities because of the influence 

 of seasonal changes on power supply. The per- 

 formance of an Allen Moore cell was studied, and 

 the results show that increasing the effiuent flow 

 increased the cathode current efficiency, the volt- 

 age and the energy efficiency, although the last 

 decreases as high flows are reached. Increasing 

 current density decreases the efficiency and 

 increases the voltage at the rate of 0.01 volts per 

 amp. per square root. For 92 per cent, current 

 efficiency the salt conversion is very close to 50 

 per cent. For a given energy efficiency the flow 

 is directly proportional to the current density. 

 For a given current efficiency the flow is pro- 

 portional to the current density above 75 amp. 

 but falls off rapidly below that. 



Physical properties of dental cements: Paul 



POETSCHKE. 



Filtration formulas: W. K. Lewis. The for- 

 mulas hitherto proposed for filtration in chamber 



