19151 Isomerism of the Hydkojuglons 191 



tion. The statements of H. Erdmann^ on its formation by 

 means of chromic acid are erroneous. P. Friedlaender and S. 

 Silberstern^ obtained juglone by coupling 1, 8-aminonaphthol 

 with diazobenzenesnlfonic acid, followed by reduction and oxi- 

 dation. It was suggested that 1, 8-dihydroxynaphthalene might 

 serve as the raw material. 



The formation of monoazo dyestuffs from it proceeds most 

 smoothly in aqueous alcohol solution if less than the theoretical 

 quantity of the diazo compound is employed. 5g Dihydroxy- 

 naphthalene are dissolved in 300cc alcohol and coupled with 

 2.5g diazobenzenesnlfonic acid at a low temperature. After 

 twelve hours the alcohol is boiled oif and the dyestuff is salted 

 out with a little salt. To remove any dihydroxynaphthalene it 

 is washed with alcohol. It crystallizes from dilute alcohol in 

 garnet red quadratic plates. It dissolves considerably in water 

 but is difficulty soluble in alcohol. 



0.2060g Substance gave 0.1398g BaS04 

 Calculated for CeHioOg^gS: S, 9.32 

 Found S, 9.32 



The dyestuff is stirred up with much excess of sulfuric acid 

 and zinc dust is added until it is decolorized. The filtrate which 

 is still strongly acid is cooled and treated with an excess of 

 ferric chloride in o^ne portion. Juglone crystallizes out, 1.4g 

 being obtained from 3.0g dyestuff. The product, however, was 

 seldom pure. After recrystallization the yield usually dropped 

 to 0.5g to 0.6g. 



a- AND ^-HYDROJUGLONE 



a-Hydro juglone, whether it is obtained from green walnut 

 shells, or by the reduction of juglone or by the transformation 

 of )S-hydrojuglone, differs in one point from the statements of 

 Mylius, for we find that the melting point of all our preparations 

 is 148° whereas Mylius found it to be 168-70°. We do not 

 doubt but that a satisfactory explanation of this difference will 

 yet be found. 



"Ann., 247,358 (18SS). Also the statement in Beilstein, III, .SSO, that jug- 

 lone according to M. Kawalski is formed from a-^fiphthol In alkaline solution 

 by means of atmospheric oxygen, is incorrect. This author, Ber. 25, 1660 

 (1802) is describing here the ordinary hydrosynaphthoquinone. 



'Monatsh., 23,513 (1902). 



