one-tenth milligram. Although the particles of CuSCN are much smaller 
than those of AgCl, they were retained by the pores of the crucible. 
III. Determination of Al in Alo(SO,4)3 as Al,O3. 
The effect of high temperature upon the Alundum crucible as well as 
its applicability for filtration of gelatinous precipitates, were discovered by 
this analysis. Chemically pure Al.(SO,);.18H,O was dehydrated by gentle 
dessication and final heating for 4% hours at 140°. <A solution was prepared 
such that each 50 ec. ec. contained .2154 grams of Al.(SO,)3. Al(OH); was 
precipitated from the hot solution in the presence of NH,Cl by just a sufficient 
amount of NH,OH. After boiling, stirring and allowing to stand, the pre- 
cipitate was filtered through the crucible previously heated in the flame of a 
blast lamp for several minutes, and washed with water containing small 
amounts of NH,Cl and NH,OH. In seven attempts however in spite of all 
precautions and lengthened time of treating the precipitate, part was drawn 
through the crucible with the filtrate. The last three determinations were 
made with an entirely new solution of Als(SO.)3, each 50 ¢. ¢. containing 
.2001 grams. 
EFFECT OF HEATING ON THE CRUCIBIE. 
Except in one case where the change was negligible, the crucible lost 
in weight consistently from one analysis to the next. The first crucible was 
pulled apart by suction while cleaning with water following the third analy- 
sis, and the second in exactly similar fashion after the fourth analysis in 
which it was employed, showing that the material becomes extremely brittle 
after heating several times in the blast lamp. 
IV. The determination of Ba in BaCl. as BaSO,. 
The extremely small size of the particles of BaSO, under ordinary con- 
ditions recommended a further test of the crucible. The pure BaCl. was 
thoroughly dried by heating three hours at 140° and a solution made such 
that 50 c. ce. contained .2007 grams. The hot solution slightly acidified with 
HCl was treated with pure dilute H.SO, while vigorous stirring was main- 
tained for five minutes, after which the BaSO, was allowed to settle for five 
minutes. 
Percent Ba in BaCl, cale. 65.96 found (1) 65.86 
(2) 65.98 
(3) 65.79 
The crucible was washed with water under suction and maintained 
