Lenher—Gravimetric Determination of Tellurium. 1283 
Te required 
.1607 gm. 
.1609 
.1609 
.1609 
Te obtained 
.1617 gm. 
.1613 
.1615 
.1613 
Unless the acidity in this precipitation is ten per cent, the tel¬ 
lurium is not likely to he completely precipitated or it will 
be precipitated in a very fine state of division. The solution 
should also be hot in order to secure satisfactory precipitation. 
SIMULTANEOUS PRECIPITATION BY MEANS OF SULPHUR DIOXIDE 
AND HYDRAZINE. 
By bringing both sulphur dioxide and hydrazine into a 
tellurium solution the whole of the element is thrown out of 
the solution almost instantaneously. 
The solution should have an acidity of 5 to 10 per cent and 
it is desirable to have the solution in a high degree of concen¬ 
tration. The solution is brought to boiling and 15 cc. of a 
saturated solution of sulphur dioxide is added, then 10 cc. of 
a 15 per cent solution of hydrazine hydrochloride and again 
25 cc. of the sulphur dioxide solution. The solution is boiled 
for a few minutes when the elementary tellurium will settle 
in such a way that it can be rapidly washed. The liquor is 
then brought on a platinum Gooch filter and washed with hot 
water until all of the chlorine is removed. The precipitate is 
then washed with 15 cc. of alcohol and the crucible and con¬ 
tents dried at 100-105 degrees. 
The following results were obtained by the process as out¬ 
lined above, using a 20 per cent solution of hydrazine hydro¬ 
chloride with sulphur dioxide. Tellurium dioxide was used 
for the analysis: 
Te required Te obtained Error 
. 1731 gm. . 1735 gm. +. 0004 
.2065 . .2068 +.0003 
.1638 .1641 +.0003 
.1608 .1608 - 
