Synthesis of Sugar 181 



Jii contact with peroxides of Ba or Sr, and water, polymerised 

 .formaldehydes are catalytically changed into- the simple form, and 

 .much heat evolved. 



Tliere appears to be some uncertainty as to the real nature of 

 "paraformaldehyde," and as to how best to obtain it in pure 

 form. 



If a saturated solution of formaldehyde is evaporated by rapid 

 boiling to i its bulk, or a 30°/ to i its bulk, and then allowed to 



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cool, it sets as a white waxy solid. A solution containing 175 

 90°C., then giving off water and CH^O, recondensing as a solution 

 grams of CIIo'O yielded 122 grams of this solid. It melt.s at 

 of CHjO. or escaping as gases. In a desiccator or in air it slowlj" 

 loses water and CHjO ; after three weeks in a desiccator, losing 

 36% of its weight. If heated to just over 100° c.c. it boils, and 

 .after all the water has been driven off the residue sets to a harder 

 waxy solid, Avith a specific gravity slightly greater than the hydrate 

 {1.2). Ihis gives off CH^O vapour when heated. 



Apparently the first solid obtained is the polyhydrate. This is, 

 however, unstable. After two to three weeks in a dessicator, fre- 

 quently exhausted by a Geryck pump, a considerable loss of water 

 and CH^O takes place (nearly 40%), and the residue sublimes on 

 heating. The solid lost on the average 0.8% of its weight daily, 

 until 38% has been lost, by which time the daily loss liad' fallen to 

 0.2O//. 



Botli the polyhydrate and the " paraformaldehyde," when in 

 mass, remain incompletely dissolved in cold ether, alcohol or water, 

 even after three days, but in hot water or alcohol dissolve rapidly. 

 On cooling the alcoholic solution, a larger proportion of white solid 

 separates out, which blackens and gives a smell of ether, with warm 

 strong HflSO^, and decomposes on heating. It is apparently a 

 compound of CH|,0, with alcohol. 



In the intermediate condition between hydrate and C.^H'^O.,. 

 changes to CH^O when heated in water to 130°C. Samples of 

 CjHeOa prepared in various ways, were all found to dissolve 

 slowly, after prolonged heating in excess of boiling water,, when in 

 the form of a fine powder. Large pieces, however, give for a con- 

 siderable time the appearance of being insoluble. 



In the intermediate condition between hydrate and CjHgOg. 

 it dissolves more readily in hot water than CjHgOg. melts partiallv 

 before subliming, and sublimes into oily drops, which set to a 

 white wax on cooling. When conversion is complete the C3H^0, 

 sublimes without melting, and deposits as a white solid. Xcs'^^^A/ 



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