140 Mr. W. Sutherland. [July 26, 



Each particle in a suspension of a globulin might, therefore, be called a 

 molecule, but with no advantage. In each such particle, however, a certain 

 pattern is repeated in three-dimensional space. In a colloid this pattern 

 is the real subject of the chemist's study, just as the molecule is in 

 crystalloids. Because of its importance, I propose to call this pattern a 

 semplar. An imaginary case will enable the theory to be presented in a 

 definite form. The nitrogen of NH 3 acts trivalently, but it can act also 

 with pentad valency. In the old phraseology two of the bonds of N in 

 NH3 were said to satisfy one another. Now, in Helmholtz's theory, valency 

 is the number of electrons associated with an atom. I have proposed 

 to consider variable valency as due to the existence of opposite electrons 

 in the atom showing it,* and for convenience of notation and printing 

 I have proposed to denote the positive electron by f- and the negative by b. 

 Thus both the triad and pentad valencies of N are expressed by writing it 

 #Nb 4) because i and f, can coalesce to form a doublet #b, in which each 

 electron almost completely neutralises the chemical activity of the other. 

 On the same principle the symbol of the hydrogen ion is H$, so that in 

 NH 3 there are three doublets #b chemically effective and one ineffective. 

 I have shown that these doublets and others are the cause of cohesion and 

 rigidity. In a crystal of frozen NH 3 the molecules are all separate, each 

 affecting its neighbours by the action of these doublets upon one another. 

 But imagine each ineffective doublet of N to be made effective, so that 

 preaches out to unite with \y of a neighbour 1ST, then every molecule of 

 NH3 becomes chemically linked with two of its neighbours, it becomes a 

 semplar, and the whole crystal becomes a mesh of such semplars. Under 

 certain conditions it could retain its crystalline form. This imaginary 

 example explains the nature of a colloid on the present theory, and shows 

 how the transition from crystalloid to colloid can be continuous with 

 occurrence of crystalline colloids. The formation of polymers is due to 

 ineffective doublets becoming effective, though generally the linking up of 

 molecules is restricted to groups of m molecules, where m measures the 

 amount of polymerisation. The most important case is that of water, which 

 I have shownf to be a mixture of (H 2 0)3 trihydrol, found pure in ice, and 

 of (H 2 0) 2 dihydrol. In water and other polymers we have the simplest 

 instances of semplars. When m, the measure of polymerisation, becomes 

 large and indefinite, it gives us the colloid state, in which chemical forces 

 between neighbour semplars produce effects of the same order as those 

 between the separate doublets of molecules in the solid state. Before 



*■ ; Phil. Mag.,' [6], vol. 3, p. 161. 

 t 'Phil. Mag.,' [5], vol. 50, p. 460. 



