44 BULLETIN 1187, IT. S, DEPARTMENT OK AGRICULTURE. 
of the test. Standing for a longer time than prescribed above does 
not appear to affect the results; in fact, the filtration may be dis- 
pensed with entirely if the solution is allowed to settle after the 
second shaking until perfectly clear, which usually requires at least 
24 hours. 
If an approximate result is sufficient for the purpose, such may 
be obtained by carefully pipetting off the clear, supernatant gasoline 
solution before the second shaking. The results thus obtained are 
about 10 per cent lower than by the standard method given above. 
PEKAR COLOR TEST. 
Place 10 or 15 grams of the flour on a rectangular glass plate 
about 12 centimeters long and 8 centimeters wide, and pack on one 
side in a straight line by means of a flour trier. Treat the same 
quantity of the standard flour used for comparison in the same 
manner, so that the straight, edges of the two flours are adjacent. 
Carefully move one of the portions so that it will be in contact with 
the other, and " slick" both with one stroke of the trier, in such a 
manner that the thickness of the layer diminishes from about 0.5 
centimeter at the middle of the plate to a thin film at the edge, and 
the line of demarcation between the two flours is distinct. Cut off 
the edges of the layer with the trier, to form a rectangle. Carefully 
immerse the plate with the flour in water for one minute. Place 
in drying oven at 100° C. for about 2 hours or until a rich yellow 
color develops. 
TOTAL SUGARS— PREPARATION OF SOLUTION.™ 
Place 12 grams of material in a 300 cubic centimeter graduated 
flask. If the substance has an acid reaction add 1 to 3 grams of cal- 
cium carbonate. Add 150 cubic centimeters of 50 per cent alcohol by 
volume (carefully neutralized), mix thoroughly, and boil on a steam 
bath for one hour, using a small funnel in the neck of the flask to 
condense the vapor. Then cool and allow the mixture to stand 
several hours; preferably allow it to stand overnight. Make up to 
volume with 95 per cent alcohol (neutral in reaction) , mix thoroughly, 
allow to settle, transfer 200 cubic centimeters to a beaker with 
pipette, and evaporate on steam bath to a volume of 20 or 30 cubic 
centimeters. The presence of a trace of alcohol is not harmful. Do 
not evaporate the solution to dryness. Transfer the contents of 
the beaker to a 100 cubic centimeter graduated flask, washing 
thoroughly with water. Add enough of a saturated solution of 
neutrallead acetate (60 grams of salt to 100 cubic centimeters of water) 
to produce a flocculent precipitate, and 'allow to stand 15 minutes. 
At this point the solution may safely stand overnight, if desired. 
Make up to the mark with distilled water and pass through a folded 
filter, carefully saving all the filtrate, to which add enough anhydrous 
sodium carbonate to precipitate all the lead, allow to stand 15 minutes, 
and pour on an ashless filter. Over 75 cubic centimeters of filtrate 
should be obtained. Test the filtrate for lead with a small quantity of 
dry sodium carbonate, and if any precipitation occurs add more anhy- 
drous sodium carbonate and refiltcr. 
-o Official and Tentative Methods of Analysis of the Association of Official Agricultural Chemists. Re- 
vised to Nov. 1, 1919. Compiled from p. 94, par. 56; p. 90, par. 52; p. 79, pur. _':: p. 78, par. L'.">; p. 95, 
