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254 - QUEENSLAND AGRICULTURAL JOURNAL. [1 Sepr., 1897, 
Numerous practical determinations have shown that the specific gravities 
given in the following table correspond to certain starch-contents :— 
é Eoite Per Cant ' Coat Per Cont, 
TOGO UMMA Tree er me D:D 1:096 is2ies sch CT TES 
LOG2@ ee os RPO 1:098 NY 4... | Wee 
NOY, os a ae 1 1:100 sien lobe LS 
TR0GC Mere ek eh 910°9 1:102 wa a 
ni. Be a aan any 1°104, Re ear, IK 
L070 Bees MR TT's 1/106 all, 42) SOT 
1°72 Se ree, 10-2 1:108 aie eh ct pl ECOG 
IRV Fe OKA wa UY 1110 Peer ce eri, Sil fl 
LOE Sate ee ease 1112 TAMER re iE 
IK Cie Gol a Pee AEG 1114 a3 eh LAOS 
12050 ee a TU) 1116 MME cys + RHE 
1082 ear Se me eel 4-5 1:118 Memon sy eke 
OSA tee) oe beet em 5-0 1:120 ee irs). Ha 
WU ae ars ea 1122 S40.” Wee 
KS eS ee UD) 1124, Lon fe MN Oda 
THO ee, 1:126 A.d* Sl en 
OOZES te me Pe 81618 1:128 nl Sara 
TE oy ee els 1:130 Jigs ay) eR 
The specific gravity of a given sample of potatoes can be found by using 
the following methods :— 
1. A vessel (preferably glass) of about two gallons capacity is filled with 
a strong brine solution containing about 1 part of salt by weight to 8 parts of 
water. 
A sample of potatoes, say 12 to 16 of the tubers, after having 
been washed and dried, are thrown into this salt solution; and will be found to 
be floating. Pure rain water is now slowly added, under stirring, to reduce 
the strength of the salt solution until only one-half of the tubers remain 
floating. When this point is reached, the specific gravities of the solution and 
of the potatoes are the same. The specific gravity of the salt solution is now 
simply determined with the help of a hydrometer or salinometer. [A similar 
method is used to determine rapidly the sugar-contents of sugar beets. ] 
2. A few of the porte are weighed in a bag made of very fine netted 
silk, and then weighed again suspended and immersed in water. ‘This second 
weighing will be less than the first weight found, the difference in the two 
weights being the weight of a volume of water equal to the volume of the 
potatoes; and from these two weights the specific gravity is easily calculated 
from the formula given above. 
An accurate balance is required for this method—in fact, special balances 
have been constructed for the purpose; and therefore this method is perhaps 
not within the reach of a practical farmer. 
3. The last method is not only quick, very accurate, but requires only 
very little apparatus. This method was first recommended and perfected by 
Professor Stohmann. 
