Lenher—Gravimetric Determination of Tellurium. 1281 
Later r Gutbier 3 described tbe precipitation of tellurium by 
means of hydrazine as a method for its determination. His 
mode of procedure is to dissolve telluric acid in warm water in 
a porcelain dish covered with a glass cover and add by means 
of a pipette a 10 to 20 per cent solution of hydrazine hydrate. 
A dark blue almost black color is noted and after heating a short 
time, elementary tellurium is precipitated in a flocculent con¬ 
dition, the liquid becoming colorless. He continues the addi¬ 
tion of hydrazine hydrate until the fluid is no longer colored by 
further addition of the reagent. 
Experimental. 
Precipitation by hydrazine .—In our hands the method of 
Gutbier gave fairly good results. The facts were noted, how¬ 
ever, that the addition of an excess of the hydrazine does not 
at once precipitate all of the tellurium. It is preferable to 
add a small amount of the precipitating agent from time to 
time. This necessitates several hours for complete precipita¬ 
tion. The following results were obtained by Gutbier's 
method in hydrochloric acid solution: 
Te0 3 
.2247 gm. 
.1988 
.2006 
.2056 
Te required 
.1795 gm. 
.1588 
.1608 
.1643 
Te obtained 
.1790 gm. 
.1577 
.1596 
.1637 
Precipitation by sodium acid sulphite .-—In order to com¬ 
pletely precipitate the tellurium by this reagent from a hy¬ 
drochloric acid solution of a tellurous compound, the solution 
must contain excess of the reagent and must be allowed te 
stand in a warm place for twenty-four hours. In the follow¬ 
ing experiments the sodium acid sulphite was prepared freshly 
for this purpose by passing sulphur dioxide into a solution of 
sodium carbonate. It has been our experiejnce that when 
sodium acid sulphite which has not been freshly prepared is 
used for the precipitation of tellurium, that the precipitated 
element frequently contains sulphur. 
sBer. 34, 2724. 
