“ 
1 Supr., 1897.] QUEENSLAND AGRICULTURAL JOURNAL, 255 
The apparatus required consists of a cylindrical glass 
vessel holding about one gallon, the upper part of which is 
ground fairly horizontal; two metal strips (M and m in 
Figs. I. and II.), having each in the middle a pointer of 
brass and a pipette (P) and a burette (B) necessary to 
measure accurate volumes of water. 
To start the operation the vessel is filled with water 
antil the surface just touches the point of the longer pointer, 
which is placed on the top of the vessel. When this point 
is nearly reached, water is only slowly added with the help 
of the pipette. The accurate point is easily and sharply 
determined as soon as the reflected picture of the needle- 
point and the point itself touch each other. Now the 
strip M is replaced by strip m with the shorter pointer, 
and water is now slowly added from a burette, which 
allows the operator to ascertain easily the volume of 
water added, until the surface again touches the point 
of the needle. This operation is only done once for all 
determinations, and gives the volume V of water neces- 
sary to fill the glass vessel between the end of pointers 
on M and m. 
Jo carry out the determination of starch in a 
sample of potatoes, the vessel is again filled as in Fig. I. 
to pointer M; and then 10 to 12 tubers, which were 
previously well washed and dried with a soft cloth and 
also weighed (total weight G) as carefully as possible, 
are cautiously put into the water contained in the 
vessel. Spirting of the water has to be avoided. The 
water, of course, will rise in the vessel, and now, by 
putting the strip m on, it will be found that a much 
smaller volume of water V (Fig. II.), which is carefully 
added with the burette B, will be necessary to raise 
the water to the level of the point of the needle on the strip m. The specific 
gravity is easily calculated by the formula— 
_ Specific gravity = 7 g 3 
By looking up the specific gravity in the table given above, the actual 
content of starch in the sample of potatoes is found. - 
