26 Wells—COompounds containing Lead and extra Lodine. 
I have also prepared the compound, exactly according to 
Groéger’s directions, as a reddish-brown precipitate, and after 
the product was apparently free from intermixed iodine and 
air-dry, it was dried for three days, spread out in a very thin 
layer under a bell-jar well charged with solid potassium 
hydroxide. This product gave the following results on analysis: 
Calculated for 
Found. — PheI;(OH)s. 
Watercolors 1°80 1°66 
This result indicates that Grdger overlooked water in his 
compound, and that his precipitate is identical with the erys- 
tallized product. 
I have observed the formation of this salt under various con- 
ditions when alcoholic solutions containing lead acetate and 
iodine, and in some cases potassium iodide also, were diluted, 
but the purest crops have been obtained only when the ingre- 
dients were used nearly in the proportion which Groger recom- 
mends, and also when the aleoholic mixture has been allowed 
to stand for the proper period. The compound cannot be 
recrystallized from water, alcohol or mixtures of the two 
liquids, and it seems probable, as Gréger suggests, that it is 
formed by the decomposition of some other compound by 
water. This view does not conflict with the fact that it was 
prepared, as described above, by the evaporation of certain 
alcoholic solutions, because these always contained water which 
increased in proportion to the alcohol as the evaporation went 
on. The presence of an acetate seems to be indispensable to 
its production, for | have made a number of experiments using 
lead nitrate instead of the acetate with no indication of its 
formation. It seems probable that a soluble compound closely 
related to Johnson’s salt is formed at first and that this yields 
Gréger’s compound by the action of water. 
I have made unsuccessful attempts to prepare a bromide 
corresponding to Gréger’s salt, and my attempts to replace a 
part of the iodine in it by bromine have also failed. 
Conclusion.—The two compounds which have been re-inves- 
tigated, 5Pb(CH,CO,),.3KI.6I and PbI,. PbO .31.H,O show 
no evident relation to each other nor to the compound 2PbI,. 
3KT.1.4H,0, which I have previously described, except that 
all of them are of complicated composition and they all con- 
tain extra iodine without showing evidence of the existence of 
lead tetraiodide. Classen and Zahorski’s quinoline salt, previ- 
ously referred to, seems to furnish the only evidence of the 
existence of this higher iodide in combination. 
Sheffield Scientific School, New Haven, Conn., March, 1895. 
