74 
CHEMISTRY: BAXTER, GROVER AND THORVALDSON 
One marked difference, however, exists between the two cases. In the 
experiments by Baxter and Wilson from 4 to 5 grams of salt were dis- 
solved in a liter of water, whereas in our first experiments 8 to 9 grams 
of salt were dissolved in the same volume. In other words the basic 
salt precipitates only at high concentrations 
As in the case of the bromide, uncertainty exists as to whether the 
basic salt is formed during the fusion of the slightly damp material, even 
in the presence of a high hydrochloric acid concentration, or whether it 
is due to hydrolysis duriag solution. Since, however, we found that 
lead chloride which has been crystallized from dilute hydrochloric acid 
solution, when dissolved in enough hot water to yield a solution nearly 
saturated at room temperature (about 10 g. per liter), yields a similar 
insoluble compound which dissolves readily in dilute acid and contaias 
chlorine, the latter explanation seems the more probable one. 
More direct evidence that the fused chloride is neutral was obtained 
as follows : Chloride which had been crystallized from very dilute hydro- 
chloric acid solution was dried in a vacuum at room temperature. 
Weighed portions were then fused in a current of hydrochloric acid gas 
and the loss in weight due to water was found. The fused portions 
were compared with silver in the usual way, and at the same time other 
weighed portions of the vacuum-dried material were similarly analyzed. 
After correction for the moisture retained by the unfused material, both 
fused and unfused salt were found to possess the same composition. 
Further evidence that the fused salt is free from basic chloride, is 
afforded by the agreement of the chloride analyses among themselves, 
as well as with the results of the bromide analyses. 
In dissolving the fused salt for analysis the precipitation of the 
basic salt was prevented as with the bromide by adding a small amount 
of nitric acid to the hot water in which the chloride was dissolved. It 
was proved experimentally that no chlorine is lost in this way. 
Furthermore, as with the bromide, the fused chloride usually contained 
a trace of black insoluble matter, in spite of the utmost care in the puri- 
fication of the salt and in the preparation of the hydrochloric acid gas in 
which the salt was fused. Since, however, this residue was collected upon 
a weighed platinum-sponge crucible, and since, after it had been weighed, 
a correction was applied, no appreciable error from this source could have 
occurred. The average per cent of the black residue found in the chloride 
was essentially the same as that found in the bromide. 
The source of the lead material used in the preparation of the lead 
bromide and a portion of the lead chloride is unknown to us. Both 
commercial metal and commercial lead nitrate were employed. Be- 
