< 612 ) 
and 57°/ 0 for TeS, so that the composition came very near to that 
of TeS, but with an excess of tellurium. 
The telluric acid was not reduced in the cold; the TeO, dissolved 
in hydrochloric acid yielded a black precipitate with 71.2% of 
tellurium and therefore situated between TeS and TeS,. 
The basic nitrate is rapidly attacked by H,S, but only at the 
surface; on the other hand it dissolved completely in boiling ammo- 
ninmsulphide, which solution, after being concentrated in vacuo at 
40°, and allowed to crystallise in a vacuum desiccator over CaO, 
yields hard, pale yellow needles of a compound which may be 
recrystallised in vacuo without decomposition. The colour of the 
needles is greenish-yellow: they dissolve in water to a clear, yellow, 
strongly alkaline solution, which rapidly oxidises when exposed to 
the air; the crystals also soon turn black on exposure. The analysis 
gave a varying tellurium-content according to the method of prepa¬ 
ration ; in one instance were found 20.1% (NH 4 ), 42% T» and 
37.9®/„ S, which leads to the formula (NH 4 ) s Te 3 S 7 1 ). 
In an analogous way the potassium compounds were prepared from 
the tellurite and tellurate with H 2 S, by solution of the precipitate in 
the solution saturated with H 2 S, dr by solution in KOH, and by 
conduction of H,S through it; the solutions were evaporated in vacuo, 
and were then left to crystallize over calcium oxide. Apparently the 
same yellow compounds are formed in all these cases, which crystal¬ 
lize in rosette-shaped aggregates of hard, fine needles, which in a 
humid condition smell strongly of H 2 S, and yield clear, readily 
oxidisable solutions. Also the solid salts themselves oxidise rapidly, 
in which they become greenish yellow, and finally perfectly black. 
On close investigation the colour appears to assume different shades, 
even if to all appearances the same mode of preparation is used. 
Attempts to find a constant composition for these salts, have been 
unsuccessful; successively it was found to be: 35.4% Te (calculated 
J ) The analysis of these complexes is a very tedious operation. If tellurium only 
has to be estimated and no sulphur, the reduction process with S0 2 or NaHSO s 
is still to be preferred. In our case, the tellurium had to be precipitated from a 
boiling, strongly ammoniacal solution with hydrazine hydrate, which reduction 
proceeds very slowly and also incompletely, and had often to be repeated half a dozen 
times. The last traces of still dissolved tellurium betray themselves on heating by 
the fine steel blue colour of the colloidal tellurium present; this is generally 
completely precipitated on rendering the liquid acid, and by way of control the 
solution may then be heated once more with ammonia and hydrazine hydrate. 
The tellurium was collected on a weighed filter dried at 100° and weighed as 
such. The S0 3 was weighed as BaS0 4 , the K as KGl or KC10 4 theNH s as NH 4 C1. 
For obvious reasons the analysis of the barium salt is a very tedious affair. 
