Recipes for making murexide from uric acid
The translation was performed with the help of Babel Fish
Preparation of the murexide(1). |
On a large scale as well as in the laboratory, this operation is delicate and undoubtedly difficult to carry out. The conditions for success must be determined with care and precision, because of the extreme facility with which this substance changes, as soon as one exceeds the suitable proportions of the reacting bodies and the desired degree of heat.
We will speak here only about the industrial process. In the beginning, the murexide was sold as paste, then as powder, but currently it is delivered as crystals.
Murexide as paste, dyes with carmine purple.
This acid solution is evaporated with the water bath, in enamelled cast iron boilers, at a temperature which should not exceed 80. It is coloured little by little in red and finishes, while thickening, by becoming of brown dark. The paste hardens on cooling.
During the concentration, the urea breaks up, and the incipient ammonia which is formed reacts on the mixture of alloxane and alloxantine, to give the murexide. It is more advantageous to neutralise the free nitric acid, before heating, either by ammonia, or by soda carbonate; in this last case it is formed soda purpurate.
Paul Schützenberger, Traité des matières colorantes, comprenant leurs applications à la teinture et à l'impression et des notices sur les fibres textiles les épaississants et les mordants publié sous les auspices de la Société industriele de Mulhouse et avec le concours de son comité de chimie, vol 1 pp 408-409, Paris, 1867.
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