BOOK X. 441 



The first of these consists of one libra of verdigris and three-quarters of 

 a libra of vitriol. For each libra there is poured over it one-sixth of a libra 

 of spring or river water, as to which, since this pertains to all these com- 

 pounds, it is sufficient to have mentioned once for all. The second com- 

 position is made from one libra of each of the following, artificial orpiment, 

 vitriol, lime, alum, ash which the dyers of wool use, one quarter of a libra 

 of verdigris, and one and a half unciae of stibium. The third consists of three 

 librae of vitriol, one of saltpetre, half a libra of asbestos, and half a libra of 

 baked bricks. The fourth consists of one libra of saltpetre, one libra of alum, 

 and half a libra of sal-ammoniac* 



The furnace in which aqua valens is made' is built of bricks, rectangular, 

 two feet long and wide, and as many feet high and a half besides. It is 

 covered with iron plates supported with iron rods ; these plates are smeared 

 on the top with lute, and they have in the centre a round hole, large enough to 

 hold the earthen vessel in which the glass ampulla is placed, and on each side of 

 the centre hole are two small round air-holes. The lower part of the furnace, 

 in order to hold the burning charcoal, has iron plates at the height of a palm, 

 hkewise supported by iron rods. In the middle of the front there is the 

 mouth, made for the purpose of putting the fire into the furnace ; this mouth 

 is half a foot high and wide, and rounded at the top, and under it is the 

 draught opening. Into the earthen vessel set over the hole is placed clean 

 sand a digit deep, and in it the glass ampulla is set as deeply as it is smeared 

 with lute. The lower quarter is smeared eight or ten times with nearly liquid 

 lute, each time to the thickness of a blade, and each time it is dried again, 

 until it has become as thick as the thumb ; this kind of lute is weU beaten 

 with an iron rod, and is thoroughly mixed with hair or cotton thread, or with 

 wool and salt, that it should not crackle. The many things of which the 

 compounds are made must not fill the ampulla completely, lest when boiling 

 they rise into the operculum. The operculum is likewise made of glass, 

 and is closely joined to the ampulla with linen, cemented with wheat flour 

 and white of egg moistened with water, and then lute free from salt is spread 

 over that part of it. In a similar way the spout of the operculum is joined 

 by linen covered with lute to another glass ampuUa which receives the distilled 

 aqua. A kind of thin iron nail or small wooden peg, a little thicker than a 

 needle, is fixed in this joint, in order that when air seems necessary to the 

 artificer distilling by this process he can pull it out ; this is necessary when 

 too much of the vapour has been driven into the upper part. The four air- 

 holes which, as I have said, are on the top of the furnace beside the large 

 hole on which the ampulla is placed, are Ukewise covered with lute. 



*This list of four recipes is even more obscure than the previous list. If they were 

 distilled, the first and second mixtures would not produce nitric acid, although possibly some 

 sulphuric would result. The third might j'ield nitric, and the fourth aqua regia. In view 

 of the water, they were certainly not used as cements, and the first and second are deficient 

 in the vital ingredients. 



''DisMlation, at least in crude form, is very old. Aristotle (Meteorologica, iv.) states 

 that sweet water can be made by evaporating salt-water and condensing the steam. 

 Dioscorides and Pliny both describe the production of mercury by distillation (note 58, p. 

 432). The Alchemists of the Alexandrian School, from the ist to the 6th Centuries, men- 

 tion forms of imperfect apparatus — an ample discussion of which may be found in Kopp, 

 Beitrage zur Geschichte der Chemie, Braunschweig, 1869, p. 217). 



