The following Table exhibits several good analyses of the potato:—
| Sort. | Fibrine. | Starch. | Veg. album. | Gum. | Acids and Salts. | Water. | Analyst. | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Red potatos | 7 | ·0 | 15 | ·0 | 1 | ·4 | 4 | ·1 | 5 | ·1 | 75 | ·0 | Einhof. |
| Id. germinated | 6 | ·8 | 15 | ·2 | 1 | ·3 | 3 | ·7 | — | 73 | ·0 | — | |
| Potato sprouts | 2 | ·8 | 0 | ·4 | 0 | ·4 | 3 | ·3 | — | 93 | ·0 | — | |
| Kidney potatos | 8 | ·8 | 9 | ·1 | 0 | ·8 | — | — | 81 | ·3 | — | ||
| Large red do. | 6 | ·0 | 12 | ·9 | 0 | ·7 | — | — | 78 | ·0 | — | ||
| Sweet do. | 8 | ·2 | 15 | ·1 | 0 | ·8 | — | — | 74 | ·3 | — | ||
 | |||||||||||||
| Potato of Peru | 5 | ·2 | 15 | ·0 | 1 | ·9 | 1 | ·9 | 76 | ·0 | Lampad. | ||
| Potato of England | 6 | ·8 | 12 | ·9 | 1 | ·1 | 1 | ·7 | 77 | ·5 | — | ||
| Onion potato | 8 | ·4 | 18 | ·7 | 0 | ·9 | 1 | ·7 | 70 | ·3 | — | ||
| Onion Voigtland | 7 | ·1 | 15 | ·4 | 1 | ·2 | 2 | ·0 | 74 | ·3 | — | ||
| Onion cultivated in the environs of Paris | 6 | ·79 | 13 | ·3 | 0 | ·92 | 3 | ·3 | 1 | ·4 | 73 | ·12 | Henry. |
POTASH, or POTASSA. (Potasse, Fr.; Kali, Germ.) This substance was so named from being prepared for commercial purposes by evaporating in iron pots the lixivium of the ashes of wood fuel. In the crude state called potashes, it consists, therefore, of such constituents of burned vegetables as are very soluble in water, and fixed in the fire. The potash salts of plants which originally contained vegetable acids, will be converted into carbonates, the sulphates will become sulphites, sulphurets, or even carbonates, according to the manner of incineration; the nitrates will be changed into pure carbonates, while the muriates or chlorides will remain unaltered. Should quicklime be added to the solution of the ashes, a corresponding portion of caustic potassa will be introduced into the product, with more or less lime, according to the care taken in decanting off the clear lye for evaporation.
In America, where timber is in many places an incumbrance upon the soil, it is felled, piled up in pyramids, and burned, solely with a view to the manufacture of potashes. The ashes are put into wooden cisterns, having a plug at the bottom of one of the sides under a false bottom; a moderate quantity of water is then poured on the mass, and some quicklime is stirred in. After standing for a few hours, so as to take up the soluble matter, the clear liquor is drawn off; evaporated to dryness in iron pots, and finally fused at a red heat into compact masses, which are gray on the outside, and pink-coloured within.
Pearlash is prepared by calcining potashes upon a reverberatory hearth, till the whole carbonaceous matter, and the greater part of the sulphur, be dissipated; then lixiviating the mass, in a cistern having a false bottom covered with straw, evaporating the clear lye to dryness in flat iron pans, and stirring it towards the end into white lumpy granulations.
I find the best pink Canadian potashes, as imported in casks containing about 5 cwts., to contain pretty uniformly 60 per cent. of absolute potassa; and the best pearlashes to contain 50 per cent.; the alkali in the former being nearly in a caustic state; in the latter, carbonated.
All kinds of vegetables do not yield the same proportion of potassa. The more succulent the plant, the more does it afford; for it is only in the juices that the vegetable salts reside, which are converted by incineration into alkaline matter. Herbaceous weeds are more productive of potash than the graminiferous species, or shrubs, and these than trees; and for a like reason, twigs and leaves are more productive than timber. But plants in all cases are richest in alkaline salts when they have arrived at maturity. The soil in which they grow also influences the quantity of saline matter.
The following Table exhibits the average product in potassa of several plants, according to the researches of Vauquelin, Pertuis, Kirwan, and De Saussure:—
| In 1000 parts. | Potassa. | |
|---|---|---|
| Pine or fir | 0 | ·45 |
| Poplar | 0 | ·75 |
| Trefoil | 0 | ·75 |
| Beechwood | 1 | ·45 |
| Oak | 1 | ·53 |
| Boxwood | 2 | ·26 |
| Willow | 2 | ·85 |
| Elm and maple | 3 | ·90 |
| Wheat straw | 3 | ·90 |
| Barb of oak twigs | 4 | ·20 |
| Thistles | 5 | ·00 |
| Flax stems | 5 | ·00 |
| Small rushes | 5 | ·08 |
| Vine shoots | 5 | ·50 |
| Barley straw | 5 | ·80 |
| Dry beech bark | 6 | ·00 |
| Fern | 6 | ·26 |
| Large rush | 7 | ·22 |
| Stalk of maize | 17 | ·5 |
| Bastard chamomile (Anthemis cotula, L.) | 19 | ·6 |
| Bean stalks | 20 | ·0 |
| Sunflower stalks | 20 | ·0 |
| Common nettle | 25 | ·03 |
| Vetch plant | 27 | ·50 |
| Thistles in full growth | 35 | ·37 |
| Dry straw of wheat before earing | 47 | ·0 |
| Wormwood | 73 | ·0 |
| Fumitory | 79 | ·0 |
Stalks of tobacco, potatos, chesnuts, chesnut husks, broom, heath, furze, tansy, sorrel, vine leaves, beet leaves, orach, and many other plants, abound in potash salts. In Burgundy, the well-known cendres gravelées are made by incinerating the lees of wine pressed into cakes, and dried in the sun; the ashes contain fully 16 per cent. of potassa.