Dr. Bottger on the Extraction of Selenium. 445 



yellow colour ; obtained in pieces, by igniting the hydrate, it is of 

 a honey-yellow colour and transparent. Its salts are white. 

 From their solutions zinc precipitates the metal in white lustrous 

 laminae. The hydrated oxide is a white voluminous precipitate 

 like alumina, quite insoluble in ammonia and the fixed alkalies. 



Sulphate of indium was obtained in indistinct crystals. It is 

 more soluble and more difficult to crystallize than the zinc sul- 

 phate. Nitrate of indium readily crystallizes from an acid solu- 

 tion, in stellate groups of prisms. 



Sulphide of indium is precipitated by sulphuretted hydrogen 

 from an acetic acid solution as a yellow slimy precipitate, which 

 dries up to reddish-brown brittle pieces. The presence of strong 

 acids prevents the precipitation. The clear yellow precipitate 

 produced by sulphide of ammonium is dissolved in an excess of 

 the precipitant when warm. On cooling, the sulphide is again 

 deposited, probably as hydrate. 



Winkler found the atomic weight of the metal to be somewhat 

 less than that found by the discoverers (37*128). He determined 

 it by converting the nitrate into oxide by ignition. He found 

 the number 35*918 as the mean of three determinations. 



Dr. Bottger describes* the following simple method of ob- 

 taining selenium from the residue of the sulphuric-acid works. 

 The mass is freed from acid by repeated washings with water; 

 it is then boiled with a concentrated solution of sulphite of soda 

 until it has become quite black in colour, owing to the presence 

 of lead. The solution is then filtered through a double filter- 

 paper, and the filtrate is allowed to drop into dilute hydrochloric 

 acid. The selenium, which has been dissolved up by the sulphite, 

 is then immediately precipitated in thick vermillion-coloured 

 flakes, which, in case any foreign matters adhere to them, may 

 be perfectly purified by being again subjected to the same 

 treatment. 



Marignac has investigated a number of niobium compoundsf, 

 both analytically and crystallographically. Hose described a 

 fluoride of niobium which he called Unterniobfluorid. He consi- 

 dered it to be the fluoride of an allotropic modification of the 

 metal niobium, Unterniobium, HnbFl 3 ; Marignac has investi- 

 gated a number of double salts of this body, all of which cry- 

 stallize well, and exhibit simple ratios of composition. 



The analysis shows that this fluoride contains three atoms of 

 fluorine. The double salts are isomorphous with the correspond- 



* Zeitschrift fur Chemie, vol. i. p. 528. Journal fur praht. Chemie, 

 vol. xciv. p. 439. 



t Liebig's Annalen, July 1865. 



