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148 mingled with the metal, than ammonia was developed, which rendered the turmeric paper brown, the original yellow re-appearing by the application of heat to the part.

Still anxious to obtain a potash which should be unexceptionably free from any source of nitrogen, I heated a portion of potash with zinc, endeavouring to exhaust anything it might contain which could give rise to the formation of ammonia: it was then dissolved in pure water, allowed to settle, the clear portion poured off and evaporated in a flask by boiling; but the potash thus prepared gave ammonia, when heated with zinc, in hydrogen gas.

With regard to the evidence of the nature of the substance produced, it was concluded to be ammonia in the experiments made in hydrogen, from its changing the colour of turmeric paper to reddish-brown; from the disappearance of the reddish-brown tint and reproduction of yellow colour by heat; from its solubility in water, as evinced by the greater depth of colour on moist turmeric paper than on dry; from its odour; and from its yielding white fumes with the vapour of muriatic acid. When formed in open tubes, its nature was still further tested by its neutralizing acids and restoring the blue colour of reddened litmus paper; by its rendering a minute drop of sulphate of copper on a slip of white paper deep blue; and also, at the suggestion of Dr. Paris, by introducing into it a slip of paper moistened in a mixed solution of nitrate of silver and arsenious acid, the yellow tint of arsenite of silver being immediately produced.

These experiments upon the production of ammonia from substances apparently containing no nitrogen, will call to mind that made by Mr. Wood house, of Philadelphia, on the action of water on a calcined mixture of charcoal and potash, during which much ammonia was produced ; and also the strict investigation of that experiment made by the President of the Royal Society during his inquiries into the nature of elementary bodies. Sir Humphry Davy found that when one part of potash and four of charcoal were ignited in close vessels cooled out of contact of the atmosphere, pure water admitted to the mixture, and the whole distilled, small quantities of ammonia were produced. That when the operation was repeated