[ J 37 ]

pipe, four feet long or more, which is to be secured bythe same lute as the juncture of the head and receiver :the pipe allows a free passage to the air or unconfinablevapours, while little or nothing of the more sluggish acidfumes will arise so high. The hole in the receiver may-be made, by pasting on it a piece of thick leather, havinga hole of the intended size cut in it, then filling the cavitywith emery, and turning round in it a steel instrument,with a hollow in the point for retaining the emery, till theglass is worn through.

A gentle fire being made under the pot, the receiversoon grows warm, and appears covered with dewy drops,which are the more watery part of the mixture. The re-ceiver beginning to grow cool again, the fire is to be gra-dually increased, till yellow or reddish fumes appear, andwhen these cease, it is to be further urged by degrees, tillthe pot becomes red hot, and nothing more can be forcedover.

This process is nearly the fame with that commonlyfollowed in the way of business ; differing little otherwisethan in the size of the vessels, and the quantity of thematerials used at once. But as the effect of the vitrioldepends wholly upon its acid, and as the acid of sul-phur is the same, and is now to be procured at a verycheap rate, the most advantageous way 0/ making spiritof nitre or aqua fortis is, to use the acid spirit instead ofvitriol. Two pounds of oil of vitriol are to be mixed withan equal quantity of water, in a stone-ware vessel, by alittle at a time ; for if the acid is added all at once to thewater, the mixture becomes so hot, as to be apt to makethe vessel crack. Three pounds of nitre being put into aglass retort, the mixture is to be poured on it through along-necked funnel, that none of the vitriolic acid mayadhere to the neck, and foul the nitrous spirit as it di-

T * slils.