8 BULLETIN 1390, U. S. DEPARTMENT OF AGRICULTURE 
not altered by either hydrochloric acid or sodium hydroxide. Potas- 
sium hydroxide, however, produces a yellow flocculent precipitate. — 
Naphthol yellow S dissolves in concentrated sulphuric acid to form 
a yellow solution, which becomes brighter upon aauielen with water. 
hen reduced with zine dust and acetic acid the solution is decolor- 
ized, but, upon contact with the air, it is reoxidized, with the pro- 
duction of a salmon color. 
In 1879 the following patents for the preparation of naphthol 
yellow S were issued: German patent 10,785 (5); British patent 
5,305 (5). In 1880 the following were issued: French patent 134,632 
(5); United States patent 225,108 (5). <n 1882 German patent 
20,716 (66) and British patent 5,692 (40) were issued. In 1883 
United States patent 289,543 (40) was issued. In 1887 British 
patent 11,318 (39) was issued. 
TARTRAZINE 
Tartrazine (C,sHy»N,O.S,Nasz), a yellow dye, may be classed as an 
azo dye, or, more properly, as a pyrazolone dye (8, 11, 18, 30, 36, 
65, 73, 77). Several methods for its preparation are given in the 
literature (82, 64, 69). The intermediates used differ according to 
the method. The principal methods are by the interaction of 
phenylhydrazine-p-sulphonic acid and dioxytartaric acid and by 
treating phenylhydrazine-p-sulphonic acid with oxalacetic ester, 
coupling the product with diazotized sulphanilic acid and hydrolyz- 
ing the resulting ester with sodium hydroxide solution. It is re- 
ported also that it may be produced by coupling diazotized sulpha- 
nilic acid with oxalacetic ester, su ee the product so formed 
with phenylhydrazine-p-sulphonic acid and hydrolyzing the resulting 
ester with sodium hydroxide solution. The first method is the 
simplest of operation and the one which is generally used. Care 
must always be taken that either the intermediates are transformed 
completely in the process of manufacture or the unchanged portions 
are removed completely by purification of the dye. 
Tartrazine, a yellow-orange powder, is soluble in water. The 
resulting golden-yellow solution is not altered by the addition of 
hydrochloric acid, but becomes redder when sodium hydroxide is 
added. The dye dissolves in concentrated sulphuric acid to produce 
an orange-yellow solution, which becomes yellow when diluted with 
water. Knecht (33) and Meyer (57) discuss its application as a dye. 
In 1885 the following patents for the preparation of tartrazine 
were issued: German patent 34,294 (6); British patent 9,858 (6); 
French patent 169,964 (6); United States patent 324,630 (6). In 1887 
British patent 8,504 (10) was issued. In 1888 German patent appli- 
cation B-8,432 (10) was issued. In 1893 British patent 5,693 (76) 
was issued. In 1897 German patent application B—20,084 (6) and 
British patent 765 (6) were issued. 
Table 6 lists the analytical determinations which should be made 
upon tartrazine, the methods to be used in analysis, and the purity 
specifications (70). 
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