New Blue Color.

Scientific American 19, 9.11.1861

The following is from the Paris correspondent of the Photographic News, London: -

The production of new coloring materials is certainly one of the most remarkable events in the chemical science of the present day; and in this particular coal tar has played the most prominent and important part. M. Ruhlmann has just made public his discovery of a new blue color obtained from cotton-seed oil. This color is chemically pure; burned on a slip of platinum it leaves no ashes; every effort to obtain it in a crystalline state has failed. At a temperature of 68° Fah. it is soluble in alcohol of 90° only in the proportion of 1,30 per 100, and in 12 per 100 in pure ether; by the aid of heat it is dissolved more freely, to be deposited in a granulated state upon cooling.

In cold alkaline solutions it is insoluble, but by a long ebullition a small quantity is dissolved, which slightly colors the liquid green.

The new color is slightly soluble in chloroform, and in sulphide of carbon. In contact with concentrated sulphuric acid, it is dissolved, and assumes a purple color. Upon adding water to this solution the blue color reappears, and is completely precipitated. Boiling phosphonic, hydrochloric, and acetic acids have no effect upon it.

The reducing agents generally, such as nascent hydrogen, sulphurous avid. the protoxides of iron and of tin, and of arsenious acid, do not affect the splendor of the new color, while the oxydizing agents, such as nitric acid, chromic acid, perchloride of iron, chlorine, bromine, iodine, destroy it immediately upon contact.

The new color is obtained by keeping the cotton oil at a temperature of 212°Fah., for five or six hours, with 3 to 4 per 100 of concentrated sulphuric acid. This contact of oil and acid must be prolonged until the green color of the oil is changed into a deep blue color. The blue substance thus obtained contains 48 per 100 of fatty acid it retains a little free sulphuric acid and some sulphate of soda or sulphate of lime. Repeated washings with warm water separate these latter products. and the separation is still more complete when, after washing in water, the blue substance is dissolved in alcohol, and afterward precipitated by water, which retains only a trace of it, but which separates the acid and the sulphate's which escaped the washing. In order to separate the fatty body the blue substance must be washed many times successively in naphtha, which also dissolves a little of the blue color so long as any of the fatty body remains in the mixture, but which dissolves only a trace of it when these washings have been several times repeated. Analysis shows its composition to be C₃₄ H₂₄ O₈ = C 69.87 H 8.22 O 21.91 — 100.00

It is difficult to avoid regarding this substance as a new definite organic compound, which combines with nitric acid, chloride, iodine and bromine.

The best mode of practically applying this now pigment remains to be discovered; but when we consider that it resists the action of the most powerful acids, viz., concentrated phosphoric and sulphuric acids, like indigo, and of other agents which destroy the color of indigo, such as boiling perchloride of tin, and muriatic acid, it may be expected that indigo and prussian blue have encountered a formidable rival in this new blue.