71 
as not to be decomposed by any except very potent agents, 
such as cfdorine, bromine, or nitric acid. It has not hitherto 
been supposed possible to effect its decomposition by means 
of fermentation or putrefaction. 
Then, again, the author found that when very small 
quantities of indigo blue are reduced according to Fritzsche’s 
method, which consists in acting on it with alcohol, grape 
sugar, and caustic soda, the colouring matter does not make 
its appearance again when the solution is exposed to the 
atmosphere. The liquid yields no deposit and remains 
yellow and transparent. This fact is also difficult to account 
for, since it is usually supposed that by the combined action 
of reducing agents and alkalies indigo blue merely takes up 
an atom of hydrogen and then dissolves, and by the action of 
oxygen is again precipitated unchanged and undiminished in 
quantity. By the continued action of a large excess of 
alcohol and grape sugar, together with caustic soda, the author 
succeeded in causing several grammes of indigo blue to dis- 
appear entirely. That the effect was due to the combined 
action of alcohol and grape sugar, not to that of one or 
the other only, was proved by subjecting a small quantity 
of indigo blue to the action of grape sugar and caustic 
alkali in watery solution, and another portion to the action 
of alcohol, protoxide of tin, and alkali. Reduction of course 
took place in both cases ; but, though the solutions were 
boiled for some time, the colouring matter was in each case 
precipitated again on exposure to the air, apparently 
undiminished in quantity. Since, by the action of caustic 
alkalies on grape sugar, acetic and formic acids are formed, 
it occurred to the author that the effect produced by the sugar 
