nd heat in a boiling water bath for 2.5
hours. Cool, nearly neutralize with sodium hydroxid solution, and make
up to 500 cc. Mix the solution well, pour through a dry filter and
determine the dextrose in an aliquot. Conduct a blank determination upon
the same volume of the malt extract as used upon the sample, and correct
the weight of reduced copper accordingly. The weight of the dextrose
obtained multiplied by 0.90 gives the weight of starch.

18. _Sugars--Tentative_

See original.[186]

19. _Petroleum Ether Extract--Official_

Dry 2 grams of coffee at 100 deg. C., extract with petroleum ether (boiling
point 35 deg. to 50 deg. C.) for 16 hours, evaporate the solvent, dry the
residue at 100 deg. C., cool, and weigh.

20. _Total Acidity--Tentative_

Treat 10 grams of the sample, prepared as directed under 4, with 75 cc.
of 80-percent alcohol by volume in an Erlenmeyer flask, stopper, and
allow to stand 16 hours, shaking occasionally. Filter and transfer an
aliquot of the filtrate (25 cc. in the case of green coffee, 10 cc. in
the case of roasted coffee) to a beaker, dilute to about 100 cc. with
water and titrate with N/10 alkali, using phenolphthalein as an
indicator. Express the result as the number of cc. of N/10 alkali
required to neutralize the acidity of 100 grams of the sample.

21. _Volatile Acidity--Tentative_

Into a volatile acid apparatus introduce a few glass beads, and over
these place 20 grams of the unground sample. Add 100 cc. of recently
boiled water to the sample, place a sufficient quantity of recently
boiled water in the outer flask and distil until the distillate is no
longer acid to litmus paper. Usually 100 cc. of distillate will be
collected. Titrate the distillate with N/10 alkali, using
phenolphthalein as an indicator. Express the result as the number of cc.
of N/10 alkali required to neutralize the acidity of 100 grams of the
sample.

UNOFFICIAL METHODS

22. _Protein_

Determine nitrogen in 3 grams of the sample by the Kjeldahl or Gunning
method. This gives the total nitrogen due to both the proteids and the
caffein. To obtain the protein nitrogen, subtract from the total
nitrogen the nitrogen due to caffein, obtained by direct determination
on the separated caffein or by calculation (caffein divided by 3.464
gives nitrogen). Multiply by 6.25 to obtain the amount of protein.

23. _Ten Percent Extract--McGill Method_

Weigh into a tared flask the equivalent of 10 grains of th