Comparative Table of 37-inch reeds, being the standard used throughout Europe, for linens, with the Lancashire and Cheshire reeds, and the foreign reeds used for holland and cambric.
| Scotch. | Lanca- shire. | Chesh- ire. | Dutch holland. | French cambric. |
|---|---|---|---|---|
| 600 | 20 | 34 | 550 | 653 |
| 700 | 24 | 38 | 650 | 761 |
| 800 | 26 | 44 | 740 | 870 |
| 900 | 30 | 50 | 832 | 979 |
| 1000 | 34 | 54 | 925 | 1089 |
| 1100 | 36 | 60 | 1014 | 1197 |
| 1200 | 40 | 64 | 1110 | 1300 |
| 1300 | 42 | 70 | 1202 | 1414 |
| 1400 | 46 | 76 | 1295 | 1464 |
| 1500 | 50 | 80 | 1387 | 1602 |
| 1600 | 52 | 86 | 1480 | 1752 |
| 1700 | 56 | 92 | 1571 | 1820 |
| 1800 | 58 | 96 | 1665 | 1958 |
| 1900 | 62 | 104 | 1757 | 2067 |
| 2000 | 66 | 110 | 1850 | 2176 |
In the above table, the 37-inch is placed first. It is called Scotch, not because it either originated or is exclusively used in that country. It is the general linen reed of all Europe; but in Scotland it has also been adopted as the regulator of her cotton manufactures.
REFINING OF GOLD AND SILVER; called also Parting. (Affinage d’argent, Départ, Fr.; Scheidung in die quart, Germ.) For several uses in the arts, these precious metals are required in an absolutely pure state, in which alone they possess their malleability and peculiar properties in the most eminent degree. Thus, for example, neither gold nor silver leaf can be made of the requisite fineness, if the metals contain the smallest portion of copper alloy. Till within these ten or twelve years, the parting of silver from gold was effected every where by nitric acid; it is still done so in all the establishments of this country, except the Royal Mint; and in the small refining-houses abroad. The following apparatus may be advantageously employed in this operation. It will serve the double purpose of manufacturing nitric acid of the utmost purity, and of separating silver from gold by its means.
1. On procuring nitric acid for parting.—a is a platinum retort or alembic; b is its capital, terminating above in a tubulure, to which a kneed tube of platinum, about 2 feet long, is adapted; c is the tubulure of the retort, for supplying acid during the process, and for inspecting its progress. It is furnished with a lid ground air-tight, which may be secured in its place by a weight. e is a stoneware pipe, about two inches diameter, and several feet long, according to the locality in which the operation is to be carried on. It is made in lengths fitted to one another, and secured at the joints with loam-lute. The one bend of this earthenware hard salt-glazed pipe is adapted to receive the platinum tube, and the other bend is inserted into a tubulure in the top of the stoneware drum f. The opening l, l, in the middle of the top of f, is for inspecting the progress of the condensation of acid; and the third tubulure terminates in a prolonged pipe i, i, consisting of several pieces, each of which enters from above conically into the one below. The joinings of the upper pieces need not be tightly luted, as it is desirable that some atmospherical oxygen should enter, to convert the relatively light nitrous gas into nitrous or nitric acid vapour, which when supplied with moisture will condense and fall down in a liquid state. To supply this moisture in the most diffusive form, the upright stoneware pipes i, i, l, l, (at least 3 inches diameter, and 12 feet high,) should be obstructed partially with flint nodules, or with siliceous pebbles; and water should be allowed to trickle upon the top pebble from a cistern placed above. Care must be taken to let the water drop so slowly as merely to preserve the pebbles in a state of humidity. h is a stopcock, of glass or stoneware, for drawing off the acid from the cistern f. k is a section of a small air-furnace, covered in at top with an iron ring, on which the flat iron ring of the platinum frame rests.
g, g, is a tub in which the stoneware cistern stands, surrounded with water, kept constantly as cold as possible by passing a stream through it; the spring water entering by a pipe that dips near to the bottom, and the hot water escaping at the upper edge.
With the above apparatus, the manufacture of pure nitric acid is comparatively easy and economical. Into the alembic a, 100 pounds (or thereby) of pure nitre, coarsely bruised if the crystals be large, are to be put; the capital is then to be adapted, and the platinum tube (the only movable one) luted into its place. Twenty pounds of strong sulphuric acid are now to be introduced by the tubulure c, and then its lid must be put on. No heat must yet be applied to the alembic. In about an hour, another ten pounds of acid may be poured in, and so every hour, till 60 pounds of acid have been added. A few hours after the affusion of the last portion of acid, a slight fire may be kindled in the furnace k.