626 TELLURIUM. 



The neutral tellurate of potash undergoes no change in con- 

 stitution under the influence of heat, resembling in that respect 

 those tribasic phosphates, of which the whole three atoms of 

 base are fixed. The bitellurate of potash loses its water and 

 becomes yellow at a temperature under redness, and is changed 

 into a quadritellurate, which is insoluble alike in water and 

 dilute acids. Water dissolves out neutral tellurate from the 

 yellow mass. The insoluble salt is named the alphaquadritellurate 

 of potash, by Berzelius. The elements of this compound are 

 united by a powerful affinity. It is formed when hydrated 

 telluric acid is mixed intimately with another potash salt, such 

 as nitre or chloride of potassium, and the mixture calcined at a 

 temperature which should be much inferior to a red heat ; also 

 when tellurous acid is ignited with chlorate of potash, and in other 

 circumstances. Hydrate of potash dissolves the alphaquadri- 

 tellurate by fusion, and nitric acid by a long continued ebulli- 

 tion ; but in both cases the acid is found as ordinary telluric 

 acid in solution. 



Telluretted hydrogen, TeH, is a gaseous compound of tellurium 

 and hydrogen, analogous in constitution and properties to sul- 

 phuretted hydrogen. It is obtained by fusing tellurium with 

 zinc or with tin, and acting on the mixture by hydrochloric 

 acid. 



Definite sulphurets of tellurium have been obtained, corres- 

 ponding with tellurous and telluric acids. They are sulphur 

 acids. 



Two chlorides of tellurium have been formed, a protochloride, 

 Te Cl, to which there is no corresponding oxide, and a bichlo- 

 ride, Te C1 2 , No higher chloride, corresponding with telluric 

 acid, has been obtained. 



