CHEMISTRY: HARKINS, HALL AND ROBERTS 
599 
Laboratory through the kindness of Drs. John Johnston and L. H. 
Adams. The only troublesome feature of the analyses was that caused 
by the color of these salts; and the difhculties encountered were such 
that it seems advisable in future work upon these salts to determine 
the concentration of the solutions by the conductivity method, since 
that method would render unnecessary the frequent gravimetric analy- 
ses which had to be resorted to, in order to make certain that the proper 
interferometric bands were being read. 
In order to give a comparison of the results with those obtained for- 
merly, the following table is inserted, which gives a few of our values 
of the equivalent freezing-point-lowerings (At/N) at rounded concen- 
trations, upon a number of these salts, including the interesting isomeric 
salts dinitrotetrammine cobalt chloride (croceo) and dinitrotetrammine 
cobalt nitrate (flavo), which are shown by the freezing-point results 
to be of the di-ionic type. The values obtained by Werner and Herty 
and by Peterson are given within parentheses. The table also contains 
the corresponding values of the van't Hoff coefhcient or mol-number i, 
and those of the percentage ionization (including those derived from 
the conductivity-ratio) . 
While the results of Werner and Herty were very severely criticised 
by Peterson, 2 it will be seen that they are of the right order of magni- 
tude, while Peterson's own results are about 100% too large, a diver- 
gence difficult to explain. The table shows that, while for the croceo 
salt the values of Werner and Herty are only about 8% too low, for 
the hexammine they obtained values which were so high (see figure) as 
to indicate that they belong to other types of salts than is the case; 
but on the whole the deviations of their results are explained by the fact 
that they used a Beckmann thermometer, and by the fact that most 
of the cobaltammines are not very soluble, so that the measurements 
have to be made in very dilute solutions, which makes the percentage 
accuracy much less than it would be at such concentrations as are 
commonly used. 
The salts investigated are given in the following list, together with 
the number of ions which we have found that each salt produces. 
Ions 
Hexammine (luteo) cobalt chloride 
Nitropentammine (xantho) cobalt chloride. . . . 
Chloropentammine (purpureo) cobalt chlor'.ie 
Dinitrotetrammine (flavo) cobalt chloride 
Dinitrotetrammine (croceo) cobalt chloride. . . 
Trinitrotriammine cobalt 
Potassium tetranitrodiammine cobaltate 
Ammonium tetranitrodiammine cobaltate 
Sodium cobaltic nitrate 
4 
3 
3 
2 
2 
0 
2 
2 
4 
