SCIENTIFIC SUMMARY. 
317 
oxide, prepared at 350°, be raised to bright red beat in a current of nitrogen 
it shrinks together, its specific gravity is changed, it can no longer be con- 
verted into sesquioxide ; in short it possesses all the qualities of the mag- 
netic oxide produced at 1200°. The result is the same when carbonic acid 
is employed in place of nitrogen, for the experiments of Gruner in 1872 
established the fact that in a strongly heated atmosphere of carbonic acid, 
magnetic oxide alone is produced. 
Revision of the Atomic Weight of Antimony. r— Prof. J. P. Cooke has 
determined anew the atomic weight of this metal, and has devoted to that 
object much time and great care. He first found the weight of antimony 
sulphide, Sb 2 S 3 , obtained from a known quantity of antimony, taking the 
atomic weight of sulphur as 32. The red variety was dried at 180° C., and 
the grey modification in most instances at 210°. A mean of thirteen expe- 
riments, where the sulphide was dried at 180°, furnished the number 119-994, 
and a mean of eleven others where the compound was heated to 210° gave 
120-295 as the number representing the atomic weight. In each case the 
author convinced himself that no free sulphur was present, and he took pre- 
cautions to eliminate every possible source of error. In a second series of no 
less than seventeen estimations, where antimony chloride was employed, the 
atomic weight of the metal was found to be 121-94, a number which closely 
corresponds with that obtained by Dumas and Dexter. In this case, it 
should be stated, the atomic weight of chlorine was taken as 35-5, and that 
of silver to be 108. As each of the two series of experiments made by 
Cooke furnished numbers which closely correspond inter se, while the final 
results differ considerably, the author set himself to determine the atomic 
weight of sulphur. By reducing silver sulphide at a low red heat with dry 
hydrogen he found sulphur to be 31-158 if silver is 108, and 32*137 if silver 
is 107*93. In a fourth series of estimations Cooke determined the amount 
of bromine in antimony bromide, SbBr 3 , and arrived at the number 120 as a 
mean of fifteen analyses. When he employed antimony iodide he again 
obtained the number 120, if the atomic weight of iodine be taken to be equal 
to 127 and that of silver 108 ; or 119-95 when the atomic weights of those 
elements are respectively held to be 126-85 and 107*93. The correct number 
appears to be 120, and the disparity appears to have arisen from the fact that 
it is impossible to prepare antimony chloride absolutely free from oxychloride 
(“Amer. Journ. Sc.” 1878, xi. 41.) 
A new Product of the Oxidation of Lead. — Red lead, as is well known, is 
prepared by heating litharge (lead oxide) in a fine state of division to 500° 
in presence of air. The oxide slowly takes up 2-3 per cent, of its weight of 
oxygen, and is converted into an oxide represented by the formula Pb 3 0 4 . 
Dumas regarded this body as a compound of lead oxide and lead peroxide — 
2?bC + Pb0 2 = Pb 3 0 4 . 
Berzelius, on the other hand, believed it to consist of lead oxide and lead 
sesquioxide, and to resemble magnetic oxide of iron (Fe 3 0 4 ) in point of 
constitution. Although he did not succeed in isolating the sesquioxide, it 
has now been shown by Debray (“ Compt. rend.” 1878, lxxxvi. 513) that 
such an oxide can under certain circumstances be formed. When lead per- 
oxide is heated to 440° a brisk evolution of oxygen is observed to take place. 
