62 Messrs. Brainier and Watts on th 



ie 



I. Sp.gr. of Bi 2 6 = 5-917. 

 II. „ „ „ =5-919. 



Specific Gravity of Urania OsMe, — One sample of U0 3 was 

 prepared by heating the nitrate to 280°. A second one was 

 prepared by heating the hydratcd oxide to 300°. 



Sp. gr. of sample No. |=5;26| Mean=5 . 14 . sp . vol . 56 . 03 . 



In explanation of Table I. it is to be borne in mind that the 

 numbers refer to one atom of the metal in the form of oxide, 

 in order to obtain comparable numbers. Many of the numbers 

 are taken from the latest papers of Nilson and Petterson *, and 

 are found to give values for specific volumes somewhat smaller 

 than those derived from older observations. 



We only give the above values as approximate ones, be- 

 cause the material to work upon does not allow of great 

 accuracy; and we only take the first seven groups into con- 

 sideration, because the specific gravities of oxides of the eighth, 

 with the formula R0 4 , are not k 



-i? 



nown. 



A glance at the table shows us that the specific volume 

 increases steadily along the horizontal as well as down the ver- 

 tical lines. The difference between the even and the odd series 

 is particularly well defined. Some of the " typical elements," 

 especially Li, Be, Na, and Mg, can be used as representatives 

 of both series. The specific volume of an oxide, where it is 

 at present unknown, can be calculated from data obtained 

 from the values surrounding it. 



Of all the oxides which are at present known, that of lithium 

 possesses the smallest specific volume, the metal having the 

 least atomic weight. On the other hand, uranic oxide, U0 3 , 

 has the largest atomic volume, uranium possessing the greatest 

 atomic weight. 



A remarkable increase of volume is exhibited by antimony 

 and bismuth pentoxides. It should nevertheless be men- 

 tioned that Sb 2 5 seems to exist in two allotropic forms, which 

 possess quite different specific gravities. One has the sp. gr. 

 6-525 (Boullay), and the other 3'779 (Playfair and Joule) f. 

 Accordingly the specific volume is either 25 or 42. 



It appears likely that two similar modifications of other 

 oxides exist — of bismuth, for example, and of uranium oxide, 

 the second one possessing the specific volume about 30. 

 Others of the numbers given are still uncertain, that for BaO 

 for example. The values at present given for its sp. gr. 



* Ber. deut. chem. Gesell. xiii. p. 1459. 



t Clarke, ' Constants of Nature,' No. I. Our other values are also 

 mainly derived from this source. 



