370 SCIENCE PROGRESS 



successful reduction of pyrrole by means of platinum black 

 and hydrogen it is essential that all traces of oxygen should be 

 excluded. The present authors find that for the reduction of 

 phthalic anhydride the exact opposite holds ; if phthalic anhy- 

 dride dissolved in glacial acetic acid is treated with hydrogen 

 in presence of platinum black very little hydrogen is 

 absorbed unless the apparatus is opened from time to time 

 and agitated in contact with air. Under these conditions re- 

 duction proceeds smoothly with the formation of phthalide 

 and o-toluic acid and subsequently of hexahydrophthalide, 

 hexahydrotoluic and hexahydrophthalic acid. In this reduc- 

 tion of phthalic acid the oxygen ring is attacked first, and the 

 benzene ring subsequently, but in the case of phthalimide, 

 which can only be reduced by the best spongy platinum, not 

 necessarily activated by oxygen, the benzene ring only is 

 attacked with the formation of hexahydrophthalimide. 



CH, 



/ \ 



CH a CH-C(\ 



1 1 / NH 



CH 2 CH-CCT 



\ / 



CH 3 



The peculiar observation has further been made that unless 

 the platinum is thus activated by oxygen many reductions of 

 acids which would normally take place are inhibited by the 

 presence of traces of anhydrides ; thus, for example, phthalic 

 acid free from its anhydride can be reduced to hexahydro- 

 phthalic acid, but no reduction takes place if there is any 

 phthalic anhydride present. 



It was shown last year by Baudisch that when a solution 

 of glucose is boiled with ferrous sulphate and sodium carbonate 

 a dark coloured solution results which contains iron in the 

 form of an internal complex, or so-called " masked iron." This 

 solution will reduce alkali nitrites to nitric oxide and am- 

 monia or nitrobenzene to aniline. Baudisch now finds (Berichte, 

 191 8, 51, 793) that the glucose in the above solution can be 

 replaced by any aldose or ketose in general, such as dihydroxy- 

 acetone, glycollic aldehyde, laevulose, maltose, etc., but not 

 by alcohols such as glycerol or mannitol. The same property 

 is also shared by a number of autoxidisable substances such 



