( 194 ) 
minations give good results, in which the parts have been killed by 
boiling water or better by boiling alcohol. 
The quantitative estimation takes place as follows: the parts of 
the plants are killed by boiling alcohol, and are then extracted with 
warm water; the extract is treated with lead acetate, of which 
the excess is removed with sodium phosphate. The free hydroquinone 
is obtained in almost colourless crystals by extracting the liquid with 
ether. After extraction the aqueous solution is boiled for one hour 
with dilute hydrochloric acid, to hydrolyse the arbutin completely, 
and the hydroquinone formed is then again extracted by shaking 
with ether. 
In case the amount of hydroquinone was small, the estimation 
was carried out in the same way as was indicated for catechol in 
the former paper, viz. by comparing the sublimates with those of a 
standard solution. If the quantity of hydroquinone was more than a 
few milligrams, the estimation was carried out by titration with 
Fehling’s solution according to Allihn’s method, after a table of 
the amounts of copper, reduced by pure weighed-out hydroquinone, 
had been prepared as a basis of calculation. 
The isolation of methylhydroquinone was carried out by extraction 
of the ether residue with benzene, in which methylhydroquinone is 
soluble, but not hydroquinone itself. The amount of methylarbutin 
and of methylhydroquinone, however, proved to be small, so that no 
considerable error was made in calculating everything as arbutin and 
hydroquinone. The arbutin content showed considerable individual 
variation and as one specimen was too small for an experiment, the 
experiments were carried out with a large number of plants from 
the same spot. The leaves are small, so that it was impossible to 
trace the variations between day and night by the method of cutting 
the leaves in half; I therefore only determined the changes during 
the opening of the buds. 
Arbutin plays the part of a reserve material, which in Vaccinium 
vitis idaea, an evergreen shrub, is principally deposited in the leaves, 
and there increases in amount during the winter until the opening 
of the buds in May. Then the amount varies from 2—3 % f° r 
in the shade, to about 5 % for plants in the sun *). 
Before the opening of the buds no hydroquinone, or merely a 
trace, is present in the leaves, and the same applies to the stems 
and roots, which latter at this period also contain but traces of 
arbutin. With the development of the young shoots from the buds 
J ) All values calculated for dry weight. 
