C{6}H{5}N:NCl + C{10}H{7}OH + Diazo-benzene chloride, B. naphthol, NaOH = 2NaCl + C{6}H{5}N:NC{10}H{6}OH + H{2}O Caustic soda, Benzene- azo-naphthol, Water. Or, with naphthylamine and naphthol, thus:-- C{10}H{7}N:NCl + C{10}H{7}OH + NaOH = NaCl + C{10}H{7}N:NC{10}H{6}OH + H{2}O Naphthalene azo-naphthol. By the action of nitrous acid upon amido-azo bodies a group of bodies called diazo-azo compounds are obtained which contain the group N:N twice over, thus:-- C{6}H{5}N:NC{6}H{4}NH{2}HCl + NaNO{2} + 2HCl = Benzene-azo-aniline-hydrochloride, NaCl + C{6}H{5}N:NC{6}H{4}N:NCl + 2H{2}O. Diazo-azo-benzene-chloride. When this compound is combined with naphthol diazo-azo dyes are produced. C{6}H{5}N:NC{6}H{4}N:NC{10}H{6}OH. Benzene-azo-benzene-azo-naphthol. The molecular weights of the bases, phenols and chemicals employed are the following:-- 1. Hydrochloric acid, HCl--36.5. 2. Caustic soda, NaOH--40. 3. Nitrite of soda, NaNO{2}--69. 4. Acetate of soda, NaC{2}H{3}O{2}3H{2}O--136. 1. Commercial hydrochloric acid at 32 deg. Tw. contains about 365 grams of HCl in a litre, or 3-1/2 lb. in a gallon. 2. The commercial 77 per cent. soda must always be used, and for practical purposes it may be taken as pure. It is best to make a solution which contains 160 grams NaOH in a litre of water. 3. The nitrite supplied is almost chemically pure, and is easily soluble in water. In order to make a solution 140 or 290 grams are dissolved per litre. 4. Crystallised acetate of soda contains 3 molecules of water of crystallisation, and is usually somewhat moist. Instead of 136 grams 140 are taken to allow for moisture. The amount is dissolved in about 500 cubic centimetres of water. _Bases._ 1. Aniline, C{6}H{5}NH{2}--93. 2. Toluidine, C{7}H{7}NH{2}--107. 3. Alpha-and beta-naphthylamine, C{10}H{7}NH{2}--143. 4. Para-or meta-nitroaniline, C{6}H{4}NO{2}NH{2}--138. 5. Nitro-para-toluidine, C{7}H{6}NO{2}NH{2}--152. 6. Amidoazobenzene (base), C{6}H{5}N:NC{6}H{4}NH{2}--197. 7. Orthoamidoazotoluol (base), C{7}H{7}N:NC{7}H{6}NH{2}--225. 8. Alpha-or beta-naphthol C{10}H{7}OH--144. _Example of Quantities Taken._ Molecular Weight. 1. Molecule nitrite 69 grams. 2. Molecule aniline 93 " 3. Molecule hydrochloric acid 365 " 4. Molecule acetate of soda 136 " 5. Molecule of naphthol 144 " 6. Molecule caustic soda 40 "