Читать книгу Gunpowder and Ammunition, Their Origin and Progress - H. W. L. Hime - Страница 10

A. Preparation of grough from natural saltpetre.

On the bottom of a vessel pierced with “three or fower littell holes” is placed a linen cloth, “or else the end of a broom, or some straw.” A layer of nitrified earth, “a spanne thicknesse,” is laid on this, and on the earth “three fingers’ thicknesse” of a mixture of “two parts of unslacked lime and three of oke asshes, or other asshes.... And so, putting one rewe” of saltpetre alternately with one of the mixture, “you shall fill the tubbe ... within a spanne of (its mouth), and the rest you will fill with water.” The water, on percolating through the mass, drips into a brass cauldron which, when two-thirds full, is boiled “till it come to one-third part or thereabouts. And after take it off and put it to settell in a great vessell,” when it is to be “clarified and from earthe and grosse matter diligentlie purged.”

B. Boiling the solution of grough saltpetre.

The solution is then “taken and boyled of new.”

F. Use of wood-ash, animal charcoal, &c.

When the solution boils and throws up scum, it is treated with a mixture of “3 parts of oke asshes and 1 of lime, together with 4 lbs. of rock alum to every 100 lbs. of the mother liquid.” “In a little time you shall see it alaie, both clear and fair and of an azure colour.”

C. Removal of insoluble impurities.

The heavy impurities, which sink to the bottom, are got rid of by pouring the clarified mother liquid into another vessel.

G. Crystallisation.

“Take it out and put it in vessels of woode or of earth that are rough within, with certain sticks of wood, to congeal.”

I. Washing and drying.

“This same saltpeter being taken from the sides of the vessel where it congealed, and in the water thereof washed, you must lay it upon a table to drie throughly.”

F´.39 Use of wood-ash, animal charcoal, &c.

“Minding to have (saltpetre) above the common use, for some purpose, more purified, &c. (which for to make exceeding fine powder, or aqua fortis, is most requisite so to be):—take of the aforesaid mixture (F) ... and for every barrel of water you have put in the cauldron ... you must put into it five potfulls” of the mixture. “In the same quantity of water so prepared, put so much saltpeter as it will dissolve.”

D. Second boiling of the solution.

Boil the whole until it “resolve very well.”

E. Filtration.

When the scum rises, transfer the mother liquid to a tub with holes in the bottom, on which is laid a linen cloth covered with a layer of sand four finger-breadths deep.

D´. Third boiling of the solution.

The filtered liquid is boiled again “in order to make the greater part of the water seeth away.... Make it boil so much until you see it ready to thicken, pouring in now and then a little of the mixture” (F).

G´. Final crystallisation.

The mother liquid is then transferred to wooden troughs “to congeal,” for which three or four days are allowed. “After this sort thou shalt make the saltpeter most white and fair, and much better than at the first setting.”