354 



practically a constant weight. A final trial of the effect upon the weight 

 of rubbing simply with the finger was made. The crucible lost .0039 grams. 



SUMMARY OF ADVANTAGES. 



(1) The crucible was used to advantage in determining Cu as CuSCN, 

 Ba as BaSCX and Ag in AgCl when HC1 was used as the precipitating agent. 



(2) Manipulating was found to be surprisingly simple and rapid when 

 an analysis was once under way. 



(3) Nearly a constant weight was maintained by the crucible if not 

 heated over 140° when washed with water. 



SUMMARY OF DISADVANTAGES. 



(1) It was found difficult at best to wash precipitates free from pre- 

 cipitating agent, especially if the latter should be left as a solid residue upon 

 evaporation of the solution. 



(2) Suction was necessary, and, in the case of AgCl,NH 4 OH, to thor- 

 oughly cleanse the crucible. 



(3) It was found unadapted to filtration of such gelatinous precipi- 

 tates as Al(OH) 3 . 



(4) Heating six or eight times in the blast lamp was sufficient to render 

 the crucible so brittle as to be broken even by suction, and a consistent loss 

 in weight was observed. 



(5) In three cases the first use of crucibles led to results greatly in 

 error. 



(6) Abrasion or friction was found to have a marked effect upon the 

 weight of the crucible. 



(7) The ordinary digestion of fine precipitates to be filtered was not 

 avoided when it was used. 



Like the Gooch crucible therefore, the Alunduni crucible apparently 

 has only a limited field of usage but within that field it should be of consider- 

 able worth to the analyst. 



