BULLETIN 1390, U. S. DEPARTMENT OF AGRICULTURE 
18 ; 
the determination and. calcufate as directed in the first paragraph 
of this section, beginning with ‘‘ Heat to boiling and add a slight 
excess of hot 10 per cent barium chloride solution.” 
For naphthol yellow S.—Transfer to a 500 c. c. volumetric flask | 
that volume of the master solution which contains 5 grams of dye. 
Add water, if necessary, to bring to a volume of about 300 ec. ec. 
Add hot saturated potassium chloride solution to bring to the 500- 
c. c. mark. Shake frequently until practically all the dye is pre- 
cipitated. After the mixture is cold dilute with water to 500 ec. c. 
Shake and filter through a dry pe er. Using 100 c. c. of the filtrate, 
precipitate, determine, and ca nialate as directed in the first para- 
graph of this section, begining with ‘‘To 100 c. c. of the filtrate add 
500 c. c. of water and 1 ¢. c. of hydrochloric acid (1+9).” 
For guinea green 6.—Transfer to a 500 c. c. volumetric flask that 
volume of the master solution which contains 5 grams of the dye. 
Add water, if necessary, to bring the volume to 400 c.c. Add 8c. c¢. 
of strong ammonium hydroxide and 125 grams of sodium chloride 
(free from sulphates) and dilute to 500 c. c. with a saturated solution 
of sodium chloride. Shake vigorously to precipitate the dye and 
filter through a dry paper. Neutralize 200 c. c. of the filtrate with 
dilute hydrochloric acid (1+9) and add 5c. c. in excess. Complete 
the determination and calculate as directed in the first paragraph of 
this section, beginning with ‘‘Heat to boiling and add a slight excess 
of hot 10 per cent barium chloride solution.” 
SULPHATED ASH 
For ponceau 3R, amaranth, erythrosine, orange I, naphthol yellow S, 
tartrazine, guinea green B, light green S F yellowish, and indigotine.—_ 
Weigh accurately about 5 grams of dye in a weighing bottle. Trans- 
fer to a pyrex Kjeldahl flask, washing out the weighing bottle with a 
little water. Destroy the organic matter to a convenient extent by 
nitric and sulphuric acid digestion, using 15 ¢. c. of concentrated 
sulphuric acid and adding concentrated nitric acid as required. 
As most of the nitric acid is driven off lower the flame to avoid 
local overheating. Transfer the mixture to a weighed platinum 
dish and heat over a ring burner, using at first a low flame at a safe 
distance below the dish, increasing the flame and bringing it closer 
to the dish by gradual steps. Thus continue the destruction of the 
organic matter and the volatilization of the acids. Continue the 
heating until the production of acid fumes decreases and danger of 
loss of volatile metallic elements arises. If carbon remains remove 
the flame, let the mass cool a little, and add concentrated sulphuric 
acid, drop by drop, until the mass is moistened. Repeat the treat- 
ment until the carbon is burned off and the ash is white or reddish. 
Heat carefully with a blast lamp until fusion takes place with the 
production of a clear liquid free from bubbles. Cool in a desiccator 
and weigh. After deducting the weight of sodium sulphate equiva- 
lent to the inorganic sodium salts (chlorides, sulphates, carbonates, 
etc.) found in the other determinations, calculate to percentage oi 
sodium combined in the dye. Reserve the sulphates for the de- 
termination of heavy metals. 
For yellow A B and yellow O B.—In a weighed platinum dish 
place 5 grams of dye. (Yellow A B and yellow O B are so slightly 
