;t>2 



NATURE 



[October 26, 191 1 



It is well known that the method of preparing nitrous 

 oxide, which consists in heating ammonium nitrate, is not 

 exempt from danger. A new and safer method of prepara- 

 tion, which gives a pure product, is described by A. 

 Quarkaroh in the Gazzetta Chimica Italiana for Sep- 

 tember 19. It consists in heating 05 gram of nitre with 

 20-25 c - c - -°' formic acid, and collecting the gas which is 

 evolved over a 20 per cent, solution of potash, which serves 

 to absorb the carbon dioxide simultaneously formed. The 

 heating must be done carefully, and it is best to apply a 

 flame until the action just begins, and then remove it at 

 once. When the action ceases another 05 gram of nitre 

 is added to revive it, and this is continued until all the 

 formic acid is used up. The action takes place quantita- 

 tively according to the equation 



:iKNO, + 6HCO„H=N 2 + 4CO L .+5H 2 0+2HCOOK, 



and this enables the decomposition to be applied to the 

 estimation of nitrates. The action is carried out in a test- 

 tube, and the gases collected over mercury in a graduated 

 cylinder capable of taking 250 c.c. ; the volume of mixed 

 gases is first measured, and then the volume obtained after 

 absorbing the carbon dioxide by introducing 2 c.c. of a 

 concentrated solution of potash. The two measurements 

 serve to control one another. The time occupied in an 

 analysis by this method does not exceed five minutes, and 

 as the results are practically as accurate as those obtained 

 by the Schulze-Tiemann method, which takes an hour, the 

 new method is to be preferred. In a second paper it is 

 shown that the action involves initially the formation of 

 nitrous anhydride, which then acts catalytically, and 

 greatly accelerates the velocity of the change. By the 

 addition of traces of substances such as chloric acid, 

 hydrogen peroxide, or potassium permanganate, which 

 destroy nitrous acid, the decomposition of the formic acid 

 is greatly retarded ; urea behaves in the same way, but is 

 not quite so active. 



A copy has been received of the " Collective Index of 

 the Institute of Brewing," which forms an exhaustive 

 book of reference to scientific work carried out in connec- 

 tion with the fermentation industries in all parts of the 

 world. The original Laboratory Club first issued Trans- 

 actions in 1887, so that the index covers the period 1887- 

 1910. It is divided into an authors' index of 130 pages 

 and a subject index of 415 pages, figures which suffice to 

 indicate the enormous amount of work which has been 

 done in connection with fermentation. Besides the publi- 

 cation of original papers and the discussion on them, the 

 institute has included for some years appropriate abstracts 

 of scientific papers in its volumes, and great praise is due 

 to the editor and his colleagues for the efficient way in 

 which this work has been performed. As a consequence, it 

 is possible to keep more easily in touch with the scientific 

 literature of fermentation than is the case in any other 

 industry, and the collective index will make the journal 

 of the society indispensable to future workers in this field. 

 The matter is printed exceptionally clearly across the page, 

 a method which, in our opinion, is far preferable to the 

 olumns adopted by many other societies. 



A paper on the endurance of metals was read by Messrs. 



E. M. Eden, W. N. Rose, and F. L. Cunningham before 



the Institution of Mechanical Engineers on Friday, 



October 20. The experiments, which were carried out at 



Univi lege, London, took the form of determining 



bei of alternations of stress which a loaded 



ting beam could withstand before rupture. The most 



remarkable point shown in these tests is the absence of 



'.11 speed effect between 250 and 1300 alternations per 



In the experiments of Reynolds and Smith ;i very 



NO. 2191, VOL. 87] 



large and perfectly definite speed effect was found for 



speeds between 1300 and 1 alternations per minute. 



The entirely different results of the University Coll. ;;• 

 tests must be due to the different form of test and testing 

 machine. 



Some interesting figures are quoted from the report on 

 breakdowns of various generating plants by Mr. Michael 

 l.ongridge, chief engineer of the British Engine, Boiler and 

 Electrical Insurance Company, in the leading article in 

 Engineering for October 20. Two similar gas engines, 

 built by the same maker, and bearing consecutive numbers, 

 were at work 100 miles apart, and broke their crank- 

 shafts on the same day. The cause was bad design, the 

 calculated stress being 21,000 lb. per square inch. Two 

 cases of extraordinary endurance of cast iron are given, 

 in both instances used for parts to which no one nowadays 

 would venture to apply it. One of the cases was that of 

 a cast-iron crank-shaft of an engine built in 1S50. 

 Between 1850 and 1 S73 the engine made 70,000,000 revolu- 

 tions, and the stress on the neck at the beginning of the 

 stroke was 3650 lb. per square inch ; between 1873 and 

 1897 76,000,000 revolutions were made, the stress being 

 2270 lb. per square inch: between 1897 and 1910 41,000,000 

 revolutions were made with a stress of 2050 lb. per square 

 inch. The other instance noted is that of a cast-iron 

 gudgeon, which dated from before 1838. It has with- 

 stood, without fracture, at least 750 million applications 

 of a stress equal to ±1500 to 1700 lb. per square inch. 



Messrs. Reynolds and Branson, Ltd., of Leeds, have 

 issued an abridged catalogue of chemical apparatus and 

 chemicals containing additions and corrections to 

 eleventh edition of their catalogue of chemical and physical 

 apparatus. 



The Emil Busch Optical Company, 35 Charles Street, 

 Hatton Garden, London, E.C., has issued several well- 

 illustrated pamphlets giving detailed particulars of the 

 " bis-telar " objectives, of the Busch projection apparatus, 

 and telephoto lenses. 



Prof. Birkeland asks us to state that the times from 

 U.S. Coast and Geodetic Survey stations given in his letter 

 " On the Simultaneity of Certain Abruptly-beginning Mag- 

 netic Disturbances" in Nature of October 12 (p. 483.) 

 should have been in decimals of a minute and not in 

 minutes and seconds ; the correct times are thus : — 

 Honolulu, ioh. 207m. ; Porto Rico, 208m. ; Cheltenham, 

 21.9m. 



OUR ASTRONOMICAL COLUMN. 



Mars. — In No. 4530 of the Astronomische Nachrichten, 

 where M. Jarry Desloges's note concerning the brightness 

 of Libya on October 12 is now published, there is also .1 

 message from Senor Comas Sola saying that on October 1 1 

 he observed a brilliant cloud on the Libya area. 



M. Jarry Desloges also continues his preliminary account 

 of the observations made at Massegros during the present 

 opposition, and directs attention to numerous changes of 

 appearance since 1909. A number of important " canals " 

 are seen in the L. Mceris region, the lake itself presenting 

 a variegated appearance. M. Cimmerium and M. Sirenum, 

 seen under good condition- pp mosaics, while the 



L. Solis, although in a vi in, is relatively dark 



anil is surrounded bj a complicati 1 ol "canals"; 



it is constricted in the middle, and the eastern half is ever 

 the darker. Ih. " canals " around this lake appear 

 abnormal, being very broad, diffuse, and pale. The south 

 polar cap is still seen, but is very small, although at times 

 very brilliant, and the north polar cap presents very sharp 

 fluctuations of relative visibility, extent, and tone. The 

 bluish tone seen in 1909 is siill there, but seems to be 

 more brilliant wl better defined. 



