454 PHILOSOPHICAL TRANSACTIONS. [aNNO I678. 



petre 3 lb. Dantzic vitriol 2 lb. Let them be well bruised and mixed in a mor- 

 tar, and then put into a long-neck, an earthen vessel so named from its figure. 

 Then six or eight of these long-necks so filled, are placed in each side of the 

 furnace, on a range built with iron bars, of the form of a parabola, at above 

 Q inches distance from each other, and closed at the sides with bricks. The 

 upper arches are left open to put in and take out the pots. Over the said arches 

 are laid large bars of iron, and then all the top of the furnace covered with 

 loam, the body of each long-neck being exposed to the fire, the neck outward, 

 to which the receivers, whether glass or German pots, are well luted. Note 

 that if the vitriol be not Dantzic, which is made with copper, but English, 

 which is made with old iron, the water will be weaker, and make a dirty co- 

 loured verditer, and wholly spoil it ; besides, the silver will not gather so well 

 to the copper after solution, and thereby becomes black. The lute is made 

 of good loam, with some horse-dung and a little colcothar, though the two 

 former do well. The luting being well worked and applied, they make a gentle 

 charcoal fire under the pots for 3 hours, and then increase it for 3 hours more; 

 about the 7th hour they make a vehement hot fire for 4 hours, and cast in at 

 last well dried billets of the length of the furnace, whose flame surrounds all 

 the pots, and finishes the work. Next morning the receivers are carefully se- 

 parated from the long-necks. Usually this work is performed but once in 24 

 hours, though sometimes twice. 



Some refiners distil 100 lb. of the materials put into a cast-iron pot, which is 

 the best way, especially being performed after this latest invention, viz. Build 

 a furnace 2 yards high or more, and at the top place in the iron pot; to which 

 fit a head of earth, like the head of a large distilling alembic for chemical oils, 

 with a large belly, about 8 inches from the iron pot, into 3 branches; dividing 

 the middle one going straight forwards, the 2 other lateral ones obliquely ; all 

 which branches are 4 or 5 inches in diameter, and 5 or 6 long. To these 

 branches are fitted glass bodies, narrow and hollow at both ends, large and glo- 

 bular in the midst; which must be well luted on with colcothar, rags, flour, 

 and whites of eggs. To this first glass body is luted on another glass of the 

 same figure and size, and 8 ranged in order till they come to the receiver, which 

 is an ordinary gallon glass. All these rows of glasses lie on boards shelving 

 from the head to the receiver. The two upper receivers or glass bodies require 

 exceeding good luting, for the rest, ordinary lute will serve. The convenience 

 of this way is, that a little fire, and that of Newcastle coal, will do the work, 

 so that you save a long-neck for each 5 pounds of materials, and you need never 

 break or unlute any of the receivers but the lowermost. 



The aquafortis being distilled off', it is put into a large earthen pot, and there 



