48 BULLETIN 448, U. S. DEPARTMENT OF AGRICULTURE. 
ture divided into two portions. To one is first added a few drops of 
alcoholic alpha-naphthol solution, then excess of sodium carbonate; 
to the other, sodium carbonate only. With azo compounds sodium 
formate may be substituted for the hydrazin salt. 
The reactions obtained are referred to classes as follows : 
Class A — Azo dyes. — These yield on oxidation in acid or neutral 
solutions a diazo compound corresponding to the " first component^' 
of the dye. 1 The azo group remains attached to the nonhydroxy- 
lated or nonaminated residue, and it is noteworthy that with Chryso- 
phenin (No. 329), the one azo color described in the table contain- 
ing neither hydroxyl nor amino groups, the usual reaction is not 
obtained. With dis-azo colors of the type of cotton scarlet, C 6 H 5 N 2 - 
C 6 H 4 N 2 C 10 H 5 OH(SO 3 Na) 2 , the azo group between the two non- 
hydroxyl-containing residues is not readily attacked, so that a diazo- 
azo compound is formed. With dyes of class A the solution becomes 
colorless, pale yellow, or pale orange on addition of bromin. After 
adding the hydrazin sulphate the solution is colorless or pale brown- 
ish or pinkish, a tendency to show a slight coloration being more 
marked, the more nearly neutral the solution. Addition of sodium 
carbonate alone produces no marked coloration, but alpha-naphthol, 
followed by the carbonate, gives a pronounced color. It is advisable 
to add some ether to the colored mixture and shake ; since if the first 
component of the original dye was an unsulphonated amin (indi- 
cated by "e" in the table) the new coloring matter formed will be 
taken up by ether from the alkaline mixture, giving usually an orange 
solution that on being poured off and treated with a large excess of 
concentrated hydrochloric acid becomes, in most cases, violet or 
blue. If the new dye is sulphonated (indicated by "w"), it will not 
be extracted by the ether from the mixture. When desired, the 
alpha-naphthol derivative, after separation by a suitable solvent, 
may be dyed on wool or silk and further identified by the ordinary 
spot tests with acids and alkalies. See tables for solubilities and 
reactions of Orange I (No. 85), Fast brown N (No. 101), benzeneazo-a- 
naphthoL and a-naphthaleneazo-a-naphthol (serial numbers in tables : 
55, 66, 122, 123, respectively). 
Other compounds, such as a-naphthylamin, readily coupling with 
diazo compounds, may, of course, be used instead of the a-naphthoi, 
sodium acetate being substituted for the sodium carbonate when an 
amin is employed. With the simple monazo colors, the reaction seems 
almost quantitative . With benzidin dyes it takes place least smoothly. 
Class AA — Azo dyes, reacting like the preceding class in solutions 
that contain a considerable amount of free hydrochloric acid (perhaps 
one-half normal or above). — In neutral solutions other oxidation 
x Por action of halogens on azo compounds, see M. Schmidt, J. prakt. Chem. 8-4 (1912), 235. Oxidation 
by lead peroxid, Lauth, Bui. Soc. Chim. 6 (1891) III, 94; by nitric acid, O. Schmidt, Ber. Chem. Ges. 38 
(1905), 3201, 4022. See also Meldola, Proc. Chem. Soc. 10 (1S94), 118, and Trans. Chem. Soc. 55 (1889), 60S, 
and 65 (1894), 841. 
