178 



A. J. Etuart: 



of magnesium liydrate, remaining: after all the fomaldeliyde had 

 been polymerised, the appro/ximate amount required Avas esti- 

 mated. 



Using these proportions more exact estimations were made. The 

 condensing flask was provided with a condensing tube 4 ft. long, 

 which was sealed at the upper end as soon as the liquid had bten 

 brought to boiling point, and allowed to blow out to a thin safety 

 bulb. The liquid was then kept just at the boiling point for several 

 days. The liquid became brown before the end of each experi- 

 ment. 



In the presence of magnesium formate, 500 c.c. of water and 

 10 c.c. of 31.5% formaldehyde, after the addition of 23 c.c. of 

 3.5% sodium hydrate, a small amount of a white insoluble solid atill 

 remained after several days. This was not Mg H2O2, and wa& 

 insoluble in dilute acid, the liquid was faintly acid, and still con- 

 tained a small amount of CHgO. 



Using 750 c.c. of water, 15 c.c. of 31.5% CH-vO, a slight excess: 

 of magnesium formate and 40 c.c. of 3.5% NaHO, all the formnl- 

 dehyde was removed, after boiling for 22 hours, the liquid was^ 

 faintly acid, and contained a small amount of white solid, incon- 

 spicuous when suspended, but not consisting of Mg HjOg. This- 

 represents a percentage polymerisation of 58. A further test gave- 

 a polymerisation value of 57. As a small amount of the magne- 

 sium hydrate appears to form an insoluble compound, and as 

 during prolonged boiling a trace of the formaldehyde is oxidised 

 directly to formic acid, which represents a further direct removal 

 of magnesium hydrate without producing any polymerisation, the 

 polymerisation value of 57 to 58 for the divalent Mg corresponds 

 fairly well with that of 65-68 for the divalent Ca. Ba. Sr, and con- 

 trasts sharply with the values for the monovalent K and Na of 8 to 

 14%. 



Potassium. — On the basis of the conclusions given above, that 

 the relative efficiency of calcium and sodium as polymerisi ng^ 

 agents depends upon the former being divalent, and the later 

 monovalent, we should expect to find equivalent solutions of the 

 monovalent metals, sodium and potassium, exercising a very 

 much inferior polymerising action, and that in the presence of 

 calcium formate it should be a matter of indifference whether 

 sodium hydrate or an equi-molecular solution of potassium hydrate 

 was used to bring about polymerisation. 



As a matter of fact the correspondence is even more exact than 



