SAKUR.U: CONSTITUTION OF GLYCOPOLL. 2Qf) 



Addendum to the preceding paper. 



June 1894. 



Til the Vrocccilinijs of tlie Chemical Society, London, issued ]\I:iy 

 2. 18!)4. tliere a[)pe:ired an abstract of the preceding' ])aper and, \m- 

 niedi:!îe]v followino- it, a note on the same subject but from a pliysical 

 stand-point, by Dr. James Walker. Dr. Walker compared the electrical 

 conductivities of g-lycocoll, phenyl-glycocoll, hii)puric acid, and aceturic 

 acid with that of acetic acid, and found that, whilst glycocoll itself is 

 an extremely feeble conductor, its derivatives are far better conductors 

 than acetic acid. "Consequently", he says, " if acetic acid contains 

 a carboxyl grcuip, ])henylglycocine (etc.) must, a fortiori, contain 

 one." lie then concludes with the words, " If we are to trust to 

 analoo-y, thereibre, the evidence aiforded bv the electrical conduct- 

 ivitv ""oes to show that "-lycocine has not the ring constitution, 

 but the ordinarily accepted constitution represented by the fornuila 

 mi,. CH,. COOH." 



In comino- to this conclusion I cannot follow him. That 

 glycocoll derivatives, with their high dissociation constants, are to be 

 reo-arded as open-chain compounds when dissolved in water is a 

 statement from which I do not, indeed, dissent. ]>ut, then, by the 

 very same reasoning glycocoll itself must be regarded as a closed-chain 

 compound, even when dissolved in water. Dr. Walker has not a 

 word to say in explanation of the remarkable difference, which he has 

 obser\'ed, between the non-conductivity of glycocoll and the conduct- 

 ivity of its derivatives. Before attempting myself to find some ex- 

 planation for it, I wish to emphasise the point that, if the electrolytic 

 behaviour of glycocoll proves anything as to its constitution, it is that 



