The specimen of chloroform sent me by Mr. Grattan was, in July, quite colorless, and on the sides of the bottle a few minute crystals were observed. The stopper of the bottle was, however, so firmly fixed in that I could not remove it, and I, therefore, placed the bottle on the mantel-shelf in my library exposed to diffused light, for the purpose of observing the changes which its contents would undergo.
In the course of a few weeks it began to acquire a pinkish or amethystine tint, as described by Mr. Grattan. This slightly augmented in intensity for a few days, and then became somewhat paler. But for several weeks, during which it remained in the same situation, it never became colorless, though the intensity of the color was frequently changing.
The color of the liquid was precisely that of a weak solution of permanganate of potash.
Some weeks ago I placed the bottle in a dark cupboard, and at the expiration of about three weeks found that the liquid had become quite colorless. As the stopper was still immovable, I was obliged to cut off the neck of the bottle to get at the contents. I found that the chloroform had undergone decomposition, and had acquired a powerful and irritating odor, somewhat allied to, but distinct from, that of hypochlorous acid. The vapor yielded white fumes when a rod moistened with solution of ammonia was brought in contact with it, blue litmus paper was reddened but not bleached by it. A few drops of the liquid were placed on a watch glass and volatilized by a spirit lamp; they left scarcely any appreciable residue.
The crystals which lined the bottle were then examined. They were few in number, and not larger than pins’ points. They were white, and when examined by the microscope, were found to be six-sided pyramids, like the crystals of sulphate of potash. Some of them were heated to dull redness in a test tube, without undergoing any appreciable change. When heated on the point of a moistened thread in the outer cone of the flame of a candle, they communicated a violet-white tinge to the flame, characteristic of a potash-salt. They readily {119} dissolved in water, and the solution did not yield any precipitate on the addition of a solution of nitrate of baryta, showing that the salt was not a sulphate. The solution was boiled with nitric acid, and then treated with a solution of nitrate of baryta, but no precipitate was observed. Nitrate of silver produced in the aqueous solution of the crystals a white precipitate, soluble in ammonia, but insoluble in nitric acid.
Whether these crystals were in any way connected with the change of color which this sample of chloroform underwent, I am unable to determine; but I suspect not. I am anxious, however, to draw the attention of others to the subject, in the hope that larger specimens of the salt may be obtained for examination. For at present the circumstances under which chloroform frequently undergoes decomposition are very obscure. Except in this instance, I have never met with, nor heard of, any sample of chloroform which underwent these remarkable changes of color.
The chloroform was transferred into another bottle, on the sides of which a few minute crystals are now formed. But since the removal of the stopper the pink color has not re-appeared.
I have written to Mr. Grattan to obtain, if possible, further information respecting this specimen of chloroform. But he tells me he has not any more of the sample, and has no means of ascertaining by whom it was made, as about the time it was purchased of him he had in his shop parcels from London, Edinburgh and Dublin, as well as a small quantity prepared in Belfast, and he is quite unprepared to say from which of them it was taken.
I suspect that the pink color of the chloroform must have been due to the presence of manganese. If so, was this metal derived from the chloride of lime used in the manufacture of chloroform? Mr. Squire informs me that he has occasionally found the solution of chlorinated soda to become of a pinkish hue after being prepared a few days (not immediately), and that he has attributed it to some manganese carried over with the {120} chlorine gas, as he does not remember having observed this change when the gas had been passed through water before entering the solution of carbonate of soda.
If this suspicion should prove well founded, it is obvious that the purity of the chloride of lime employed in the preparation of chloroform deserves the attention of the manufacturer.