October 13, 1922] 



SCIENCE 



429 



after standing one week show a decided decrease 

 in the acid and iodine numbers and a decided 

 increase in the saponification number and melting 

 point. The percentages of unsaponifiable matter 

 remain constant. The results show that rosin 

 should be kept in lump form and powdered imme- 

 diately before the analysis is to be made in order 

 to prevent changes in its constants. 



The effects of treating materials and outdoor 

 exposure vpon the water resistance and tensile 

 strengtlt of cotton ducTc: T. D. Jantsll and 

 H. P. HoLMAN. Numerous samples of treat- 

 ed canvas were exposed to tlie weather for 

 six months under conditions unfavorable to mil- 

 dew and bacterial decay. Unexposed portions of 

 the same samples after the same length of time 

 sliowed little or no deterioration. With many of 

 the treatments developed by the Bureau of Chem- 

 istry the treated canvas showed very high water- 

 resistance after weathering. By adding certain 

 bituminous materials or mineral pigments to 

 treatments which, when used alone, gave the can- 

 ■i^as low water-resistance after exposure, the 

 water-resistance was considerably increased. With 

 all of the treatments free from pigments the 

 treated canvas gave after exposure tensile 

 strengths loiver than that of the untreated canvas 

 after exposure. The addition of mineral pig- 

 ments to certain waterproofing preparations which 

 caused decided weakening of the canvas when ex- 

 posed to the weatlier materially reduced such 

 effect in every instance and in some cases the 

 treated fabric after exposure was stronger than 

 the untreated fabric after exposure. The results 

 indicate that the addition of mineral pigments to 

 waterproofing preparations is beneficial since they 

 reduce the weakening effect of solar light and 

 heat without reducing water-resistance. 



A new form of precision hydrometer: C. W. 

 FouLK. This hydrometer consists of a glass float 

 moving freely in a glass tube carrying a suitable 

 scale. Between the float and the lower end of the 

 tube a light chain hangs in a catenary curve. The 

 float is ballasted so as to be in approximately 

 submerged floating equilibrium in the liquid to be 

 tested. The final adjustment to exact equilibrium 

 is automatically made by the action of the chain, 

 and this position of the float is then read on the 

 scale. With a properly calibrated instrument 

 density determinations accurate to one unit in 

 the fourth decimal place can be made in a couple 

 of minutes. 



Che^nical corrosion of iron silicon alloys: A. K. 

 Smalley. The desirability of using iron silicon 



alloys as universal resistant materials for chem- 

 ical construction and wherever there is a possi- 

 bility of chemical corrosion has been firmly estab- 

 lished. Their manufacture demands the use of 

 the best grades of material, the best foundry 

 practice and careful metallurgical control. Silicon 

 contents should be about 14,5 per cent. If it is 

 lower the acid resistant qualities of the metal 

 will be afCected, and if it is higher the strength 

 is lessened and many manufacturing difdculties 

 are encountered. Other specifications are given 

 in the paper. 



Furfural resins: Gael S. Miner, John P. 

 Tkickey and Harold J. Bkownlee. 



Distillation of dilute ammonia solutions: G. 

 Galingaeet. In very dilute solutions .ammonia 

 does not follow Henry's law, the volatility being 

 progressively less as dilution increases. In con- 

 sequence the complete removal of ammonia from 

 ammonia water mixtures is rendered difdcult. 

 Careful experimental determinations of the con- 

 stant of Henry's Law demonstrate that the devia- 

 tion is due to dissociation and indicate that in 

 extreme dilutions there exists a constant boiling 

 mixture. 



Causticization of soda ash: J. Harro?. Expe- 

 rimental determination is reported of the influence 

 of time, temperature and the amount and char- 

 acter of lime used in causticizing dilute soda ash 

 solutions upon the degree of conversion and the 

 rate of settling of the resultant sludge. The sig- 

 nificance of the results in design and operation of 

 causticizing plants is indicated. 



Decomposition of nitrates: W. K. Lewis and 

 G. J. Greenfield. The thermal decomposition of 

 sodium nitrate into nitrate was studied in order 

 to secure data on the temperature coeflieien-t of 

 the reaction rate constant of a completely homo- 

 geneous reaction at elevated temperatures. This 

 data was obtained, and ii was furthermore 

 demonstrated that the conversion of nitrate to 

 nitrite is reversible, the reaction equilibrium 

 shifting to the nitrate side as temperature 

 increases. In consequence the reaction rate, after 

 the reaction has progressed to an appreciable 

 extent, is decidedly retarded by the reverse re- 

 action. The decomposition itself is monomolecu- 

 lar, but the character of the reverse reaction has 

 not yet been determined. 



Potash from Icelp. VIII — Theoretical consid- 

 erations pertaining to the preparation of potas- 

 sium chloride from Icelp brines: J. W. Tueren- 

 TINE and H. G. Tanner. Kelp brine contains, 

 after rectification, potassium and sodium ehlo- 



