in which P is the total rotation observed. Upon now treating the solution of glucose with an excess of an alkaline solution of mercuric cyanide (prepared by dissolving 120 grammes of mercuric cyanide and 25 grammes of potassium hydroxide in 1 litre of water), the dextrose and maltose contained in the sample are decomposed, leaving the dextrine unaffected. A second polariscopic reading is then made, which gives the amount of dextrine present, that is
P′ = 193 d′,
(2)
from which the proportion of dextrine is calculated.
Subtracting the second equation from the first, we have
P - P′ = 52 d + 139 m.
(3)
Both dextrose and maltose reduce Fehling’s solution, the total reduction (R) being the reducing per cent. of the former (d) added to that of the latter (m). The reducing power of maltose is, however, only 0·62 as compared with dextrine, therefore
R = d + 0·62 m.
(4)