Fleta minor the laws of art and nature, in knowing, judging, assaying, fining, refining and inlarging the bodies of confin'd metals : in two parts : the first contains assays of Lazarus Erckern, chief prover, or assay-master general of the empire of Germany, in V. books, orinally written by him in the Teutonick language and now translated into English ; the second contains essays on metallick words, as a dictionary to many pleasing discourses, by Sir John Pettus ... ; illustrated with 44 sculptures.

CHAP. VII. How to purify and cleanse the raw Salt-Petre.

WHEN the Salt-Petre is thus made, and [Section. 1] the rest of the Lees drawn off, lift up * 1.1the Kettles or Trays, and turn them to one end, that the remaining Lee may run clear off; then take a great Iron Spoon such as Bricklayers use, and lift out the Salt-Petre with it, out of the Kettles or Trays, put it into a Tub, with a hole below, that the Lees may run clean off.

[Section. 2] Some Salt-Petre Boylers, (who sell the raw unpurifi∣ed Earth-Petre) they pour clean Well-Water upon it, that it may be well washed from the most part of its redness, and become white, what is run off they put again to other strong Lee, and boyl it the next boyling.

But if you will purify the raw Salt-Petre right and well [Section. 3] from its Salt and uncleanness, to become fair and white, do * 1.2it thus; When the raw Salt-Petre is a Centner or four, cause the purifying Kettle to be cleansed and dryed, pour in it so much Well-Water, that the Salt-Petre may be dissolved in it, then make a fire under it, let the water be boyling hot, and then put the Salt-Petre gently and easily in it, and turn it about with the scumming Spoon, that the Salt-Petre may be the sooner and easier dissolved.

But while you are pouring it into the Kettle, let there [Section. 4] be but little fire under, that the cleansing may remain warm, and when the Salt Petre is almost all put into the

water and melted, and the cleansing begin to boyl, then with the scumming-Spoon, put some upon the ground, and when the Salt-Petre hath set great Grains of Salt, then lift it out, which is better for it.

[Section. 3] * 1.3When this is done, and the cleansing begins to boyl, then it brings up a black scum, take that off, and take a Copper Vessel which holds near 8 Loths of strong Lees, and make it half full of the cleansing; put it in cold wa∣ter to cool it suddenly, so the Salt-Petre will begin to shoot (and this is called a Proof made) then you will see whether the cleansing be yet too strong, if it be, there will come a skin over the Proof in the Vessel, and if so, then fill more warm water into the Kettle, and keep it in such a strength, that the cleansing in the Kettle may bubble, then make a Proof out of the Vessel, and when the cleansing shoots in it, and in the midst do remain open (so that it doth not close together) then the Proof is right, but if it grows together, then fill more water, till the Proof remain open, and pour near a pint of Vinegar in the cleansing into the Kettle, which will bring up a black scum, for the cleansing will purify it self of it, and when the scum is thick, take it off, and when the cleansing hath bubled a while longer, pour in it so much good Vinegar as may keep it in continual bubling, and then take the * 1.4black off, as at first, this you may do the third time, and pour on Vinegar, till the cleansing be very clean, and do cast up no more black scum; Then take 3 or 4 loths of burnt-Allum, beaten small, and put it in the cleansed wa∣ter, stir it about, and of this the Salt-Petre useth to yield fine long slacks, and it hurts not the Salt-Petre, then pour the cleansing in the before▪mentioned high slender Tub, and cover it, that it be not cold in the Tub; let it stand an hour or two at most, thus the yellow dirt will settle it self in the bottom, then let the cleansing run out while 'tis hot, and pour it into a great wooden Tray, or great

Copper Kettle, which for coolness had need stand in the ground, and cover them warm that the Lees may begin to spring from below, else the Salt-Petre will grow first above and fall down, and so will not yield very long slacks, let it stand three or four days until it grows no more, which you may prove thus; set some of the Lees in the Copper-proof Vessels▪ if it grow no more in it, then take away the rest of the Lees, and let it clean go off, and then put the Salt-Petre with the Iron Spoon, clean out of it, into a Vessel with a hole below, that the rest of the Lees may run off, and thus you have purified Salt Petre.

The Lees which is drawn off (while it is yet salty) [Section. 4] boyl it as the other strong Lee (in making of the Salt or Lee) and from this the raw Salt-Petre will grow very well. But some use at the cleansing in the Kettle, Calx viva, by which it becoms as white as Milk, and they let it settle in the Tub, which makes the Salt-Petre very fine, but it settles not so soon or so well in the Tub, and while the cleansing stands thus strong in the Kettle, you must not make too great a fire, for if it boyl too high, you can hardly quiet it, or hinder it from running over, where∣by comes great loss, therefore it must be kept bubling with a little flame, and when the Kettle is washed, such water is to be boyled again with the strong Suds or Lees, but the scum which is to be taken off from the cleansing must be put upon the Ashes, where more Lee is to be put over Ashes, that that which is yet in it may come to profit, and when you boyl much in the Kettle, then lay upon it a hard grey stone, like the colour of Tartar, under which the Kittle useth to burn, and this is sometimes to be cleansed and separated off, with a flaming fire made un∣der it, to make it fly off, and when the Kettle is empty and clean, then you may boyl it again.

The Earth and Ashes which have been extracted [Section. 5] (whereof comes the raw weak Lee,) are to be put in

into vaults or Houses, and in four years it will be sit to use, only when you use it to make Lees, then you must (many weeks before) dig open such Vaults, that the moistness may go off, and the Sun may shine in, and of this good Lees may be made.

[Section. 6] But the old Masters do suppose, that if one could * 1.5run off the Petre in the Houses under Tylings, it would be sooner good, which is likely, for, because of too much moistness or daily rain upon it, the Salt-Petre is much spoiled, and will have only a little moistness, of which it is to be generated.

[Section. 7] * 1.6Also some of the old Masters do use among the Earth in the Lees-Tub, to mingle bits of Firr Wood, a finger long, and these they put among the Earth, with the Lees that hath been made, and set it in the vaults or Houses, and such fatness which is used in the mingling the Salt-Petre * 1.7doth also generate and multiply, and they say when it lays in a dry place, it may be used again within a year; likewise they pour upon the light poor Earth in Houses, the old decayed colours of Cloth-Makers or Dyers, or any sharp decayed colours of Waters made with Allum, yet not so often, but that such Earth may have a better beginning to a good effect. Next, they bring also Soot out of the Stoves, Furnaces and Chimnies, and mixt with the Earth, likewise the Ashes of such Lees as is made in Houses, and in the Nosel or Mouths of Ovens, where much Straw is burnt, which Ingredients do much help to a melioration, that it may sooner be used.

[Section. 8] Know this only by the way, That sometimes Earth is found which gives brown thick Lees, which of it self is too fat to make Salt-Petre of, amongst which you must mingle another Earth more brittle and lean, and with it put some made Lee over it, or else you will bring no Salt-Petre off from it fit to be washed.

How the Salt Peter is cleansed, and what Instruments

pertain to it, they are almost alike to the XXXIX. and XL. Sculptures next before, and out of the same to be seen.

Notes

• * 1.1

  Raw Salt-Petre.
• * 1.2

  To purify it
• * 1.3

  To make proofs.
• * 1.4

  To purify it again.
• * 1.5

  How Salt-Petre is ge∣nerated and spoiled.
• * 1.6

  To mingle splinters of Wood with it.
• * 1.7

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