14 BULLETIN 1390, U. S. DEPARTMENT OF AGRICULTURE 
eho 
expressions (1 +1), (1+9), etce., accompanying the names of reagents, 
the first numeral indicates the volume of strong or concentrated — 
reagent used and the second numeral indicates the volume of water 
used. 
PREPARATION OF SAMPLE 
Take a 500-gram true representative sample of the batch, or one 
that after all tests have been made will leave enough for future 
reference, should any question arise. For determinations requiring 
a dry-weight starting point, weigh the various portions in uninter- 
rupted succession, using wide weighing bottles for these and other 
weighings. Weigh out catch quantities, approximating those needed, 
keeping the bottles stoppered as much as possible. 
Without delay prepare a master solution of such concentration and 
volume as will provide for all determinations, including check - 
analyses, in which a solution of the dye as a starting point is specified. 
The concentration of the solution should be at least as great as the 
maximum required in the procedures to be followed. Aliquots, 
suitably diluted, are used in the procedures requiring lower con- 
centrations. 
MOISTURE 
For ponceau 3R, amaranth, erythrosine, orange I, naphthol yellow 
S, tartrazine, guinea green B, light green S F yellowish, and vndigo- 
tine.—Weigh about 2 grams of sample in a weighing bottle, 2 inches 
in diameter, or in an aluminum dish, 2 inches in diameter, and dry to 
constant weight by heating at 135° C. for six hours, or overnight. 
Before each weighing cooi over sulphuric acid in a desiccator. From 
the decrease in weight calculate the percentage of moisture. 
For yellow A B and yellow O B.—Proceed as directed in the fore- 
going paragraph, heating the dye to 80° C. instead of to 135° C. 
Yellow A B and yellow O B are so slightly hygroscopic that they may 
be weighed in the container on an even-weight basis. | 
TOTAL WATER-INSOLUBLE MATTER 
APPARATUS 
Wash with acid and later with water high-grade retentive asbestos 
and repeatedly elutriate it to eliminate the fine particles. 
Pour into a Gooch crucible placed in a filter flask enough asbestos 
suspension to make a mat one-eighth inch thick when packed. 
Connect the flask with a slow suction and pack the mat down evenly 
with a tamper. Remove the Gooch adele from the filter flask and — 
loosen the mat around the edges with a thin, narrow blade or pin; 
take the mat out and put it back in an inverted position, packing it 
down tightly as before. With this as a base, prepare a well-packed 
mat one-half inch thick. 
If it seems probable that the percentage of total insoluble matter 
present is lower than the maximum permitted for nonvolatile in- 
soluble matter, treat the crucible as follows: Wash with hot water, 
dry in an air oven at 135° C., cool in a desiccator containing calcium 
chloride, and weigh. Repeat until the weight is constant. 
If it seems probable that the percentage of total insoluble matter 
present is higher than the maximum permitted for nonvolatile in- 
