84 



A. J. 



Ewart : 







(CH,0).2H.,0 



Alkali 



Glucose equivalent Per cent. 

 Loss of of reducing polynierizatioit'' 

 weijjfht sujfar in terms of glucose 



2.09 gram 

 l.«3 „ 

 1.69 „ 



SrH.,0.2 0.8 grain 

 BaH^O.,-! 

 NaHO 0.5 „ 



0.63 gram 

 0.55 „ 

 0.74 „ • 



0.35 

 0.34 

 0.08 



17% 



22% 



5% 



(CH2O)., 

 1.25 „ 



BaH^O,, 1 



0.41 „ 



0.33 



26% 



111 each case the amount of alkali was sufficient to remove all 

 the formaldehyde. When sodium hydrate and the polyhydrate are- 

 pounded together, the reaction starts spontaneousl;/, and is very 

 violent. There is a heavy loss of formaldehyde vapour, and much 

 of the sugar is caramelised. For this i*eason the percentage poly- 

 merisation is less than when a boiling dilute solution of formalde- 

 hyde is neutralised with dilute sodium hydrate. 



If the reaction is started by locally warming several grams of 

 the mixture in a small distilling flask, a large amount ,of distillate- 

 is obtained without applying further heat. This consists in the 

 case of the polyhydrate (and crystalline Ba H2O2) <'f water, methyl' 

 alcohol and formaldehyde. 



If a slight excess of the polydrate is used, the whole of the 

 BaH20.2 is converted into barium fojinate. This can be obtained 

 by dissolving the residue in a little water, and adding an equal 

 bulk of alcohol. A large part of the sugar slowly settles out with 

 some barium formate. On filtering after 48 hours standing, and' 

 doubling the bulk in the alcohol, a second ppt., mainly of barium' 

 formate, is produced, which, can easily be washed and purified. 



A point worth noting is that if the finely ground polyhydrate is 

 mixed thoroughly with finely ground crystalline barium hydrate, 

 the mixture smells strongly of formaldehyde, and its temperature 

 falls 15°C. for some time. The temperature then slowly rises, but 

 not appreciably above that of the room. Ihe mixture slowly 

 develops traces of reducing sugar, but does not undergo any com- 

 plete reaction even after days in contact, until this is started by 

 heating one point of the mixture. 



A similar preliminary fall of temperature is shown with di- 

 and tri-molecular formaldehyde. If, however, tliese are mixed 

 with freslily slaked dry quicklime, or with powdered calcined 

 barium or strontium hydrates, the mixture remains dry, the fall 

 of temperature is hardly noticeable, and on heating the mixture- 

 locally the reaction does not spread. Only the parts heated turn 

 brown, and methyl alcohol distils over (yielding methyl iodide with 

 Iodine and red phosphorus). The residue contains an abundance' 



