60 A METHOD FOR MAKING METHYL VIOLET. CREIGHTON. 



salt, the amount of external heat re(iuirc(i to maintain the 

 melt at the proper temperature may be decreased, thus 

 effecting a saving in fuel. 



When oxidation is complete, the melt is gradually added 

 to a large wooden vat containing 1000 liters of boiling water, 

 in which are dissolved 13 kilograms of slaked lime. The 

 liquid is boiled, by blowing in high pressure steam, until 

 all the lumps disappear. The insoluble dou])lc salt of the 

 color base and cuprous chloride is allowed to settle and the 

 supernatant liquid runs off. This liquid contains most of 

 the salt and the phenol in the form of calcium phenate. 

 The double salt of the color base and cuprous chloride is now 

 decomposed with sodium sulphide, which converts the latter 

 into copper sulphide. To accomplish this 1000 liters^ of 

 water are run into the vat, the temperature brought to 70°C., 

 and 3.3 kilograms of sodium sulphide dissolved in a small 

 quantity of water slowly added while the liquid is stirred 

 continuously. At the end of one-half hour the temperature 

 is raised to 100°C. and the liquid boiled for five or six hours. 

 The color base and the copper sulphide are then allowed to 

 settle, the supernatant liquid run off, and the residue washed 

 twice with 1000 liters of water. 



In order to separate the color base from the copper sul- 

 phide, 1000 liters of water are run into the vat, the mixture 

 brought to boiling, 15 kilograms of sulphuric acid gradually 

 added, and boiling continued for two hours. Durmg this 

 treatment the color base dissolves, forming a deep violet 

 solution, practically all of the copper sulphide remaining 

 undissolved. After the solid material settles, the solution 

 of dye is run off into a second vat, at a lower level, and the 

 residue in the first vat is again extracted with sulphuric 

 acid. The resulting solution of dye is comliined with that 

 in the second vat. To the combined liquids sufficient sodium 

 hydroxide is added to almost neutralize the acid. The dye 

 is now salted out by the addition of sodium chloride, and on 

 cooling it solidifies to a lustrous green resinous mass. As 

 this dye contains a small quantity of the insoluble copper 

 compound, it is redissolved in 750 liters of boiling water. 

 The dye solution is passed through a filter into a third vat 

 where, on salting out, a particularly pure methyl violet is 

 obtained. The insoluble residue remaining in the second 



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