552 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
shape, and those for the saturated iodides are disposed in accordance with the 
molecular weights. 
Isopropyl iodide, as in the case of the paraffins, has at the same temperature 
always a lower coefficient than normal propyl iodide. The position of allyl iodide 
between normal and isoj^ropyl iodides, and nearer to the normal than the iso-iodide, 
is noteworthy, and again indicates the influence of constitution on the viscosity 
coefficient. 
Bromides. 
Monohromidcs .—Five monobromides were examined, viz., ethyl bromide, isopropyl 
bromide, propyl bromide, isobutyl bromide, and allyl bromide. Fig. 8 represents the 
results obtained. 
Fig. 8. 
On comparing the curves for the monohalogen compounds, the same kind of 
regularity as in the case of the iodides is apparent, both as regards their shape and 
order. The allyl curve occupies a position between those of the normal and isopropyl 
compounds as before, but is now about midway between the two. It is also to 
be noted that at the boiling-point the bromides have almost the same viscosity 
coefficient. This regularity, so marked in the case of the paraffins, was not apparent 
in the case of the iodides, but as the molecular weight falls it again asserts itself, not 
only in the case of the bromides, but also, as will be seen later, in the case of the 
chlorides. 
Dibromides. —The dibromides investigated were acetylene dibroinide, ethylene 
dibromide, propylene dibromide, and isobutylene dibromide. The results obtained 
are given in flg, 9, which also contains several of the monobroniides, and in which, 
for the sake of comparison, the curve for bromine is also inserted. 
In order to keep the curves of somewhat the same size as in previous diagrams, the 
scale of ordinates and abscissse in this flgure is two-and-a-half times as close as it 
