387 
of locating Sugars in Plant Tissties. 
is probably due to the oxidation of the reagent, for phenylhydrazine has 
not good keeping properties when freely exposed to the air. Pure glycerine 
acts as a preservative, presumably because it prevents ready access of air. 
The products formed give in glycerine brown drops of syrup (cf. foot-note 
below). 
The glycerine itself might conceivably undergo oxidation 1 by the 
action of substances present locally in the plant, in which case small 
quantities of such compounds as glyceric aldehyde or dihydroxyacetone 
might be formed, and these substances yield osazones. To examine this 
point some glycerine was oxidized with aqueous ferrous sulphate and 
hydrogen peroxide, 2 and the brown substance (osazone) resulting from the 
subsequent addition of Senft’s reagent was examined microscopically. The 
(dilute) glycerine mixture yielded drops of brown syrupy liquid, some 
opaque brown spherical masses, and some crystal clusters, the individual 
crystals of which had the form of lamellae almost as broad as long and with 
obtuse ends. To some extent such crystals resemble those yielded by 
maltose phenylosazone, and might possibly be mistaken for them if not 
closely examined. The syrup is practically indistinguishable from that of 
the maltose osazone, although rather darker in colour. 
It should be noted that the reagent itself, when tested in blank experi¬ 
ments used as controls to those in which sugar had been added, did not 
give crystals ; if properly filtered in preparation very little syrup is formed 
either. 3 
On the whole the danger of mistaking for crystals of maltose phenyl¬ 
osazone those of the osazone of an oxidation product of glycerine is small 
under the conditions in which the test is ordinarily applied. 
Salts of Phenylhydrazine. Phenylhydrazine readily forms salts with 
acids, and some of these are insoluble in glycerine and water. The hydro¬ 
chloride is fairly soluble in glycerine, the acetate also, but the oxalate is less 
soluble. The crystals, however, are in each case quite distinct in form from 
those of maltose phenylosazone. Moreover they are typically colourless, 
but might easily appear yellowish in the proximity of yellow osazones. 
While in general these crystals are distinguishable still in some arrange¬ 
ments, especially when viewed edgewise, and when at all inclined to appear 
yellow, careful examination may be necessary to determine their real 
identity. 
1 In contact with platinum black glycerine in presence of air and water produces glyceric 
aldehyde, C 0 2 and water. Watts, ii, p. 616. In contact with iron oxidizing in moist air, a substance 
like glucose is formed. Ibid., p. 617. 
2 Fenton (’ 06 ), p. 101. 
8 Cf. p. 370, foot-note 1. If, however, the reagent is old when applied, or is heated for a long 
time in presence of air, yellowish-brown liquid and crystalline or opaque masses may be formed 
after standing for some months. It is advisable to renew the phenylhydrazine hydrochloride solution 
at least once every six months, though Senft states ( 1 . c., p. 7) that the reagent may be used 
satisfactorily even if three years old. 
