766 Sir J. J. Thomson on the 



of free iodine atoms may be expected to be much smaller 

 than that of the free ammonia molecules. 



Water and the alcohols contain the hydroxyl radicle OH., 

 and the question arises, is the electrostatic doublet whose 

 moment we have been discussing carried by this radicle 

 into the various compounds, and is the intra-molecular dis- 

 sociation in these practically confined to the charging-up of 

 hydrogen and oxygen atoms in the hydroxyl radicle? If 

 this were the case, then in such compounds, if they were in 

 the gaseous state, the abnormal part of the specific inductive 

 capacity would depend on the number of hydroxyl ions only. 

 Thus, since there are the same number of hydroxyl ions in 

 water, methyl alcohol, and ethyl alcohol, the specific inductive 

 capacities of these in the gaseous state and at the same tem- 

 perature should be equal. Badeker's experiments on the 

 vapours of methyl and ethyl alcohols show that these have 

 much the same specific inductive capacities when in the 

 gaseous state, and though water seems to have a somewhat 

 higher value, the difference between them is small compared 

 with that between these substances in the liquid condition. 

 The experiments on vapours are at present not sufficiently 

 numerous to enable us to settle this point, and so we have 

 to turn to the capacities when in the liquid state, though the 

 interpretation of these is much more open to objection. The 

 specific inductive capacity of ethyl alcohol is only 26'S, while 

 that of water is 81. It must be remembered, however, that 

 since the molecule of ethyl alcohol is heavier than that of 

 water, and also because the density of alcohol is less than 

 that of water, there are fewer alcohol molecules per unit 

 volume than there are water molecules. 



In the following table I give the values of the quotient of 

 the specific inductive capacities K of a number of liquids, 

 by the number of the radicles per unit volume ; the unit is 

 an arbitrary one : — 



Radicle OH. 



K/nuuiber of radicles 

 Substance. K. per unit volume. 



Water, H.OH 817 81 



Methyl alcohol, CH 3 .OH 32-5 79 



Ethyl alcohol, C 2 H 5 OH 217 81 



Propyl alcohol, CH 3 CH 2 .CH 2 .OH. 20o 85 (Thwing) 



Glycerine ; C a H 5 (OH) 3 56*2 76 



