182 W. P. Riddell on Noleil’s Saccharimeter. 
to stand two or three minutes, then thrown upon the filter. If 
now the mixture be too highly colored to admit of observation, 
it must be discolored by filtration through bone-black, or anima 
charcoal ; special tubes for which are provided in Clerget’s very 
full and beautiful set of apparatus, which usually accompanies the 
Saccharimeter. The process will require one hour, and possibly 
the liquor may have to be passed through the bone-black several 
times. It must be remembered however, that the first portions 
(a quantity about equal to the volume of bone-black) which come 
through the bone-black, must not be employed in the observations, 
as it is found that the bone-black, until a little saturated, weakens 
the solution. The liquor is next introduced into the tube of 0 
servation, and the rotation noted as before by turning the thumb- 
screw of the compensator till the two semi-discs again exhibit a 
uniform tint. If, previous to filtering through the bone-black, 
the defecating agent has been used, the tube of 22 centimeters 
must be employed to compensate for the consequent dilution ; but 
if the defecating agent has not been used, the tube of 20 centl- 
metres must be employed. It will be observed that using the 
tube of 22 centimetres is the same in effect as adding j;th to me 
strength of the solution as determined in the tube of 20 centim. 
The number of degrees of rotation as read on the scale of the 
compensator, will give the actual per cent of pure sugar in the 
sample. The scale is so graduated that i had weighed 
16-471 grammes of pure sugar, and formed our solution 12 
the same way, by means of the matrass graduated to 100 ¢.C-s 
the rotation as indicated by the degrees of the compe 
mal or standard solution contains 164-71 grammes of pore sue" 
tain other substances which exert a polarizing influence 8° 
times to tige tight, sometimes to the left, it is desirable to disen= 
gage the influence of the same from the influence due to the cane 
sugar. For this purpose we perform what is termed the me 
Process of inversion, which affects the polarizing powet of i“ 
cane sugar only; bat which changes this from right-hand 3 
left-hand sugar. It is accomplished in the following ® 
