382 Alfred J. Etvart .- 



Calcium carhoiiate. — H. and A. Euler (Ber. d. D. Bot. Ges.,. 

 1906, 39, pp. 36 and 39), have shown that when 2 % form.aldehyde> 

 is heated with calciuni carbonate, a pentose sugar, arabinoketose- 

 is formed, together with small amounts of glycoUic aldehyde and 

 dihydroxyacetone. 



The calcium carbonate is converted into calcium formate, and 

 the reaction is possible because a portion of the former exists in 

 solution as calcium hydrate. As this is converted into formate- 

 CO2 escapes and more chalk dissociates. Hence the rapidity of 

 the action depends upon the fineness of division of the chalk. Ihus- 

 using 5 c.c. of 40 % CH2'0 to 250 c.c. water, and a slight excess- 

 of chalk, the following Avere the times taken for the removal of all 

 the formaldehyde : — 



Finely divided, freshly pptd. chalk, 70 hours' boiling. 

 Coarser portion of precipitate, 82 hours' boiling. 

 Dried precipitated chalk, 96 hours' boiling. 



In all cases the liquid is pale yellow by the second day, and is 

 distinctly browned by the time the reaction is completed. Pre- 

 sumably this is due to the presence of traces of dissociated lime- 

 caramelizing the sugar produced. 



The syrup was evaporated to a small bulk, filtered, diluted and. 

 kept for 3 days at 30°C. (a) with dry yeast, (b) with fresh yeast 

 and Pasteur's ash. Bacteria became abundant in (b). Both 

 liquids yielded a distillate which gave the iodoform test for alcohol' 

 faintly but distinctly, but which did not contain sufficient alcohol" 

 to affect the boiling point appreciably. Evidently, however, traces 

 of hexose sugars, fermentable by yeast, are formed in addition' 

 to arabinoketose. 



Magnesium carbonate is feebly alkaline, more soluble, and dis- 

 sociates more readily than calcium carbonate in solution. Hence it 

 reacts more rapidly. Using half a gram to 5 c.c. of 4-0 % CH^O and' 

 250 c.c. of water, the reaction was completedi in 4 hours boiling' 

 Avitli magnesia alba levis, and in 12 hours with magnesia alba 

 ponderosa. 



Barium carhonate. — Using a slight excess of the solid and 5 c.c. 

 of 40 % formadohyde the reaction was completed — 

 With 400 c.c. of water in 16 hours' boiling. 

 With 250 c.c. of water in 36 hours' boiling. 



The sugars appeared to be the same as with calcium carbonate,, 

 but possibly owing to the difficulty of separating all traces of the- 

 poisonous barium formate even by the use of sulphuric acid, the- 

 tests with veast were inconclusive. 



