D. CHEMISTRY AND METALLURGY. 51 



D. CHEMISTRY AND METALLURGY. 



ALUMINIUM FOR SMALL WEIGHTS. 



Dr. Phipson recomrnends very warmly the employment of 

 aluminium in the manufacture of very small weights. The 

 advantages, as set forth by him, are their immunity from the 

 inconvenience attaching; to the use of brass weights in a 

 chemical laboratory, in retaining their brilliancy untarnished, 

 and in not losing their value by oxidation. The much great- 

 er bulk occupied by a given weight, as compared with brass 

 or other metal, enables one to handle them much more read- 

 ily, and a considerably smaller weight can be used, without 

 inconvenience, than has been generally thought practicable 

 in such cases. A set used by Dr. Phipson contains fourteen 

 weights, from half a gramme to one and a half milligrammes, 

 the latter (less than the one fortieth of a grain) not being 

 very easily handled when made of any other metal. 1 A, 

 October 14,187. 



RUSTING OF IRON. 



Professor Calvert, after repeated experiments, has found 

 that pure dry oxygen does not determine the oxidation of 

 iron, and that moist oxygen has but feeble action ; also that 

 dry or moist pure carbonic acid has no action, but that when 

 moist oxygen containing traces of carbonic acid is brought 

 into contact with iron, the latter rusts with great rapidity. 

 He concludes, therefore, that carbonic acid is the agent which 

 determines the oxidation of iron, and that it is the presence 

 of carbonic acid in the atmosphere, and not its oxygen or its 

 watery vapor, that produces the oxidation of iron exposed to 

 common air. In one experiment he found that if clean blades 

 of the best quality of iron be placed in water which has been 

 well boiled, and deprived of its oxygen and carbonic acid, 

 they will not rust for several weeks ; and that if a similar 

 blade be half immersed in a bottle containing equal volumes 

 of pure distilled water and oxygen, the portion clipping in 

 the water becomes rapidly oxidized, while the upper portion 

 remains unaltered. But if to the atmosphere be added some 



