ISDUSTRIAL AND ESGINEERILY'GCHE2VISTRY
January 15, 1930
Furthermore, the Ba(OH)2 formed can take up one more molecule of water, giving Ba(OH)?.H20, which is fairly stable a t room temperature. Whereas P206is all too readily reduced, yielding the volatile trioxide, Ba(OH)2requires very high temperatures for reduction. We have found BaO especially valuable for drying such basic gases as ammonia, for which it is far superior to metallic sodium, as it yields no gas in its desiccating action. Obviously, it should not be used for drying acidic gases or gases such as SiF4,which readily hydrolyze to give acids. Use of Barium Oxide in Desiccators
A preliminary study of the use of porous barium oxide in desiccators for analytical work has shown that the rate a t which it removes moisture from the desiccator is the same as that of phosphorus pentoxide, and that it is far superior, not only in this respect, but in many others to either calcium chloride or sulfuric acid. We have therefore adopted it in place of other desiccants in the course in quantitative analysis. It is much cheaper than the calcium chloride sold for desiccators and is conveniently obtainable from the manufacturer in steel drums. Barium Oxide as a Desiccant at High Temperatures
Preliminary studies have shown that the desiccating power of barium oxide is undiminished up to high temperatures. This would be expected in view of the fact that barium hydroxide is said to be stable up to 1000" C. and probably to higher temperatures. Summary
The results of this study show that the porous barium oxide made by the low temperature reduction of barium carbonate
15
by carbon fulfils the requirements for a good desiccant. Barium oxide made by this method has a high activity and large capacity, though the oxide cannot be reactivated. Being in a solid, porous form it is easily handled, does not become sticky, and does not channel if the container is properly filled, but, on the contrary, may choke up the tube unless room for expansion is left. On account of its granular nature, as compared to the fine particles of phosphorus pentoxide, barium oxide calls for larger drying tubes to accomplish the same drying rate, but the total efficiency is about the same or slightly better than for phosphorus pentoxide. Barium oxide should be kept in sealed containers out of contact with air containing carbon dioxide and moisture. Air-slaked (carbonated) barium oxide should not be used as a desiccant, as it is then only a part'ial absorbent and its speed of absorption is low. The absorption of moisture by fresh barium oxide is complete and permits its use in accurate gas research. Barium oxide prepared by low-temperature reduct'ion of the carbonate by carbon yields no gaseous products on reaction with water. Its desiccating action remains undiminished up to 1000" C. Its use in desiccators for analytical work and for general desiccating purposes is strongly recommended. Literature Cited (1) (2) (3) (4) (5) (6)
(7) (8) (9) (10)
Baxter and Starkweather, J . A m . Chcm. Soc., 33, 2038 (1918). Baxter and Warren. I b i d . , 33, 340 (1911). Dover and Marden, I b i d . . 39, 1609 (1917). McPherson, I b i d . , 39, 1317 (1917). Man!ey, J . Chem. SOC.,121, 331 (1922). Morley, J . A m . Chem. Soc., 26, 1171 (1904); A m . J. Sci., 34, 147 (1887). Willard and Smith, J . A m . Chem. Soc.. 44, 2255 (1922). Wourtzel, J . chim. p h w . , 11, 57 (1913). Walton and Rosenblum, J . A m . Chem. So,:., 60, 1618 (1928). Y o e , Chem. S e m s , 130, 340 (1925).
Rapid Determination of Nitrogen Peroxide in Nitrogen Peroxide-Air Mixtures' Colin W. Whittaker, F. 0. Lundstrom, and Albert R. Merz FERTILIZER A N D FIXEDN I T R O C E X
IXVESTIG.4TIOsS.
active nature of the nitrogen peroxide and particularly on account of the disturbing effect of the X2O4-2S02 equilibrium upon volume measurements a t ordinary temperatures. These difficulties can be overcome, however, by a proper choice of apparatus, materials, and conditions. This paper describes such an apparatus and a method whereby the concentration of the nitrogen peroxide can be rapidly and accurately determined without resorting to weighing or titration. General Considerations
Xitrogen peroxide reacts with or is soluble in the liquids usually employed for confining gases. It attacks mercury rapidly, combines with water and various salt solutions, and reacts with most oils and organic liquids or dissolves in them. Oils with low vapor pressures usually have high viscosities a t room temperature and are handled only with difficulty in a buret. For reasons to be discussed, the gas samples in 1
Received d u g u s t 7 , 1929.
BUREAUO F
C H E X I S T R Y A S D SOILS, w A S H I S G t O N ,
D.
c.
very mobile, is not rapidly attacked by nitrogen peroxide, and has a vapor pressure low enough for use as a confining liquid. The disturbing effect of the equilibrium NnOa
* 2N02
(1)
may be avoided by measuring the volume of the gas mixture a t a temperature where the S20ris almost completely dissociated. At higher temperatures the reaction 2x02
* 2NO +
0 2
(2)
takes place and this reaction would be nearly as disturbing to volume measurements as (1). Inspection of data and curves for these equilibria showed that betm-een 150" and 160" C., a t moderate pressures, practically all the S204is decomposed into S O 2 and that the further decomposition of the N O z into S O and 0, has not yet become appreciable. Thus at these temperatures the percentage of X02 in nitrogen peroxide-air mixtures can be determined immediately, without computing
AiYA L Y T I C 9 L EDI T I O S
16
corrections for the equilibria (1) and ( 2 ) . Bodenstein ( I ) has studied these equilibria, the first in the range between 9" and 115' C. and the second between 220" and 555" C. The equilibrium constant I
