44® Miscellaneous

I poured very gently a quantity of aquaregia, made by impregnating marine acidwith nitrous vapour, on vitriolic acid, andat first it effervesced very much, and the lowerpart was. of a turbid white, while the upperpart retained its orange colour. After sometime the mixture was of a light orangethroughout. I have not yet made any fartherobservations upon it.

To try how strongly the nitrous acid va-pour was retained in this mixture of the twoacids, I exposed a part of the mixture to theheat of a common sire, in a long green glasstube hermetically sealed, and found thatthough I kept it boiling, it continued colour-less a considerable time. Afterwards a redvapour was expelled from the mixture, andat length the whole tube was filled with it.But when it was cold the vapour was allabsorbed again, and the mixture, whichwas then of a pale orange colour, becameafterwards quite colourless, as at first. Thisis not the cafe with oil of vitriol impregnatedwith nitrous vapour. For this vapoup

escapes