COLLECTING THE ARGENTIC CHLORIDE. 



39 



stream of chlorine, when the mass gained on the average only o.ooi per 

 cent. The fused argentic chloride, even before its treatment with 

 chlorine, was usually pearly and colorless. 



In any case, it is clear that this loss on fusion, which has been 

 rejected as of doubtful significance by some authors,* really represents 

 included water, and must be heeded. 



The determination of the weight of the main mass of the pre- 

 cipitate having been thus determined, attention must be directed to 

 several other precautions necessary to insure exact work. In the first 

 place, all the liquid which has passed through the Gooch crucible was 

 passed through a small washed filter, in order to collect the minute 

 asbestos shreds which even the best fibrous asbestos seems to lose under 

 pressure. This was done as soon as possible after filtration and before 

 proceeding to solubility determination. A siphon filtering arrange- 

 ment, or a large inverted flask fitted with a carefully cleansed rubber 

 stopper with two tubes arranged so as to maintain constant level, 

 obviated the tedious process of filtering by hand. The little filter was 

 finally washed free from salts, and the weight of the ignited residue 

 (minus the filter ash) added to the weight of Gooch crucible and pre- 

 cipitate. This residue usually amounted to only one or two tenths 

 of a milligram. Observation in the microscope easily showed that the 

 residue was really asbestos. 



Because it was the object of the research to test every step of the 

 processes involved, the loss and recovery of asbestos shreds was tested 

 by special blank experiments. Large volumes of water were passed 

 through empty Gooch crucibles provided with the usual mats ; and 

 the loss of each crucible after drying was found, as well as the weight 

 of shreds recovered from the filtered water. Below are given the results 

 of these blank experiments : 



In two of these experiments the loss very nearly equaled the 

 amount of asbestos found ; the other one must have been contaminated 

 by an accidental outside impurity ; but the results of the blank experi- 

 ments are enough to show that the correction is a real one and not to 

 be omitted. 



* Scott, J. Ohem. Soc. Trans., 79, 147 (1901). 



