Snelling, Henry Hunt, 1816-1897 · [New York : W.B. Smith] · leaf 221
sure to the air. Red prusiateof potassa causes a dark blue precipitateinsoluble in acids. Hydrosulphuret of ammonia producesin neutral solutions of the protoxide ofiron, a black precipitate, which by expo-sure to the air becomes of a reddish-brown. c< Gallic Acid produces a deep blue-black, in… … UR predictions are veri-|5ed with an unexpectedapidity. The future pros-pects of heliography, ofwhich we gave but an im-perfect idea in our former articles,are being revealed from day today, and only a few months havesufficed to bring about resultsto which we had assigned the termof several years.…
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