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Ultramarine Red?








In Gmelin's Handbook of Chemistry it is remarked that "Hydrogen gas
passed over ignited ultramarine, colours it light red, from formation of
liver of sulphur, hydrosulphuric acid gas and water being evolved at the
same time." On most carefully making the experiment with a sample of
native blue (the variety referred to) we did not succeed in effecting
this change: no alteration to red or even to purple took place, the only
result being that the colour was entirely spoilt, having assumed a
leaden slate-gray hue. At our request, the trial was kindly repeated by
well-known chemists, who took every precaution to ensure success.
Several specimens of ultramarine were acted upon, but in no case was a
red or anything like a red obtained, the products ranging from a
slate-gray to a drab-grey. Sufficient hydrosulphuric acid gas was
evolved to blacken paper moistened with acetate of lead, a fact which
proved that the blue had lost some of its sulphur. Seeing that not only
no red was produced, but that no tendency to red was imparted, is it
possible the change described by Gmelin occurred under exceptional
circumstances? All conversant with chemical matters will admit that
results are obtained occasionally which cannot be repeated, owing it may
be to some slight difference in the materials employed, or some slight
variation of the process. Perhaps a link, considered of no importance
at the time and overlooked, has been lost, and thus the whole chain of
proceeding becomes useless. It is, therefore, within the bounds of
probability that the red ultramarine of the great German chemist was
furnished either by a peculiar specimen of blue, or by a modified form
of the method he gives. We have noticed the subject at some length
because if a red ultramarine, brilliant and durable, could be obtained,
the colour might prove of value. A permanent artificial compound
corresponding to French blue would certainly be an acquisition.





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