178 Prof. B. Moore and Mr. T. A. Webster. 



Benedict's solution. After three hours' exposure the contents of the quartz 

 tube gave a fair reduction of Benedict's solution, while those of the glass 

 tube still gave a complete negative with this test solution. At the expiry of 

 6| hours' exposure the contents of the quartz tube gave a copious reduction, 

 but the contents of the glass tube had not yet developed any reducing 

 substance. At the end of 12 hours the contents of both tubes showed 

 reduction, those of the glass tube to about the same extent as had been 

 obtained in the quartz tube in three hours, while the contents of the quartz 

 tube now gave a heavy precipitate of cuprous oxide when tested by the 

 Benedict's solution. 



The remainder of the contents of the quartz tube were distilled at 

 ordinary atmospheric pressure almost to dryness, leaving a white solid 

 residue in the distillmg flask. The residue was taken up with warm water, 

 in which it readily dissolved, and made up to the original volume. Both 

 distillate and residue were then tested with Benedict's solution, and both 

 were found to reduce it readily, the residue containing apparently somewhat 

 more reducing substance than the distillate. Again, both distillate and 

 residue reduce neutral silver nitrate solution and mercuric chloride solution. 

 This experiment shows that the short wave-lengths are the most powerful, 

 and that the limit lies at about the shortest wave-lengths transmissible by 

 glass. 



Experiment 7. — In a somewhat similar experiment two quartz test-tubes 

 were taken, of the same dimensions as above, and the same concentration of 

 formaldehyde was employed, but around one of the tubes as thin a sheet of 

 mica as could be split off was folded so as completely to surround the 

 quartz, and held in position by two loops of thread at top and bottom. The 

 mica was so thin that it readily folded over the test-tube (about 3 cm. in 

 diameter) without cracking. Yet this thin layer of mica was so effective a 

 screen that there was not a trace of reduction after a 12 hours' exposure 

 similar to that given above in glass ; the contents of the unshielded quartz 

 tube showed a distinct reduction after two hours' exposure. 



Experiment 8. — Only preliminary experiments have hitherto been made 

 towards the identification of the substance or substances giving the 

 reductions with these metallic salts. It is natural to suppose that there 

 should be representatives of intermediate condensation products lying on 

 the path between formaldehyde and the hexoses. Pribram and Franke, in 

 the papers above referred to, believed they were able to identify glycol- 

 aldehyde arising from the condensation of two molecules of formaldehyde, 

 and Inghilleri claims to have isolated the racemic sorbose by means of its 

 osazone. 



