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POTATO. 



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The calta of potassium are characterised, 

 first, by communicating a purple colour to the blowpipe flame ; second, 

 by affording a crystalline precipitate on being mixed with excess of a 

 saturated dilution of bitartrato of aoda this tost may not succeed 

 if the [i illinium be present only in small quantity; third, by 

 giving a yellow granular precipitate on the addition of bichloride of 

 platintirn 



Xttimmtim / potaM. This is usually effected in the state of the 

 double chloride of potassium and platinum just mentioned (KC1, 

 It <_'!,(. The substance from which all other metals have been 

 siipanUnl by the ordinary system of analysis is acidulated with 

 hydrochloric acid, the bichloride of platinum added, and the whole 

 evaporated to dryness. The residue is then washed with a mixture of 

 alcohol and ether, and weighed on a tared filter ; 100 parts are equiva- 

 lent to 15-98 of potassium, or 19-26 of potash (KO). 



POTASSIUM, OXIDE OF, POTASSA or POTASH, Sftdinl Pro- 

 ftrtit* of. The preparations of potash which ore used in medicine are 

 very numerous ; but they may be reduced and spoken of under a very 

 few heads : First, those which are employed from their causticity to 

 produce counter-irritation, or to open abscesses : these are hydrate of 

 potash (potassa fun) and potash with lime (potassa cum oalce), which 

 have been already treated of. [ESCHAROTICS.] Second, those which 

 are employed to counteract acidity, namely, liquor potassrc, carbonate 

 and bicarbonate of potash, the alkalinity of which last two is dimi- 

 nished in proportion to the increase of the carbonic acid combined 

 with the alkali. Thirdly, those which possess a purgative property, 

 such as the sulphate and bisulphate of potash, the tartrate and bitar- 

 trate. Fourthly, those possessed of a diuretic property, such as the 

 acetate, and, when in small doses, the tartrate, bitartrate, the nitrate 

 and chlorate of potash. Besides these, there are the sulphide of 

 potassium, the bromide of potassium, (and iodide of potassium, which 

 possess special and characteristic qualities, which prevent their being 

 classed with any of the preceding. Chlorate of potash is of great utility 

 in the treatment of diphtheria. 



The various uses of which these numerous preparations are sus- 

 ceptible can only be explained in medical treatises : all that is proper 

 here is to caution individuals against the employment of thoae which 

 counteract acidity. These are extensively had recourse to, either in a 

 simple state or as ingredients in effervescing mixtures, for the cooling 

 effect they produce, or designedly to remove superfluous acid in the 

 stomach. Where much debility exists, and more particularly if the 

 photphatic diathesis, or disposition to the deposit of the phosphates 

 from the urine, be present, a single dose of such articles may do much 

 injury, and their frequent or prolonged use creates a worse condition 

 than that which they were intended to remedy. But this does not 

 preclude the employment of a solution of carbonate of potaah to induce 

 a coating of phosphates over the sharp angles of the mulberry or oxalate 

 of lime calculus. [OXALIC ACID.] An intelligent medical attendant 

 can alone decide on their propriety. " If I were required," says Dr. 

 Prout, " to name the medicine calculated to do the most mischief, I 

 should name the common saline draught formed of potash or soda and 

 some vegetable acid." (' Treatise on Diseases of the Urinary Organs,' 

 2nd edition, p. 145.) [CARBONIC Ann.] This remark equally applies 

 to many of the popular summer beverages, such as imperial ; and many 

 eflerveecing drinks prepared with lemon and kali. 



The property assigned to bromide of potassium, of removing enlarge- 

 ments of the spleen, is by no means clearly proved. The powers of 

 iodide of potassium have been noticed under IODINE, and those of the 

 sulphide of potassium are treated of under SULPHUR. In case of poison- 

 ing by liquor potassn or the carbonates, vegetable acids or oils should 

 be instantly administered. 



PuTASSIUMAMIDE. [POTASSIUM.] 



POTA8SIUMETHYL. [OROAXO-HKTALLIC Bonus.] 



POTATO (Solatium foierontst, Lin.). The circumstances which led 

 to the introduction of this valuable vegetable into the system of British 

 husbandry may be thus succinctly stated : 



Queen Elisabeth, in 1584, granted a patent " for discovering and 

 l-hntJTTg new countries not possessed by Christiana ; " and under this 

 sanction some ships, principally equipped by Sir Walter Raleigh, sailed 

 with him to America. Thomas Harriott (afterwards known as a 

 mathematician), who accompanied the adventurous squadron, trans- 

 mitted to England the description of a plant called Opauuet by the 

 natives of that part of North America which the courtier-like gallantry 

 ,]eigh had named Virginia. 



Harriott described the O/m-uek as having the roots round, and 

 " hanging together as if fixed on ropes, and good for food, either boiled 

 or roasted." Qerarde, in his ' Herbal,' a few years subsequently, dis- 

 tinguished the plant by a plate ; and not only confirmed the assertion 

 that it was an indigenous production of Virginia, whence he himself 

 had obtained it, but supplied some curious details of its qualities, and 

 of the various modes in which it may be dressed for the table. He 

 especially recommended it as the basis of " delicate conserves and resto- 

 rative sweetmeats," with the assurance that its flatulent effects may be 

 infallibly corrected by having the roots "eaten sopped in wine;" 



adding, "to give them the greater grace in eating, they should be 



I -.Ul with prunes." 



The honour of first cultivating the potato in Ireland, where it has ao 

 long constituted the principal food of the peasantry, has been attributed 

 to the grandfather of Sir Itobert Southwell, president of the Royal 

 Society of London, towards the clow of the 17th century. Sir Robert's 

 statement was to the effect that his ancestor had obtained some roote 

 from Sir Walter Raleigh. 



Hut the potato had been known in Spain and Portugal at an earlier 

 period, and it is from the Utter country that we most directly derive 

 the name by which we know it : this is easily shown. Although the 

 natives of North America called our plant opcnawk, those of the south, 

 more particularly the inhabitants of the mountains of Quito, called it 

 jiapas, which the Spaniards corrupted into battata : this again their 

 neighbours in Portugal softened into ba-ta-ta (da terra), to which 

 po-ta-to is a very close approximation. 



The potato was cultivated in Ireland long before its introduction 

 into Lancashire, which was owing to a shipwreck, it is said, at North 

 Meols, at the mouth of the Kibble, where the mode of propagation 

 still maintains pre-eminence, and whence the culture of this important 

 plant has gradually spread through every portion of Great Britain. 



It waa not, however, until after a considerable time that it became 

 I al.it it.],., productive, and farinaceous, or admitted into the course of 

 field husbandry. It was limited to the garden for at least a century 

 and a half after it was first planted at Youghal, and it was not until 

 1732 cultivated as a field crop in Scotland. It appears (from the 

 ' General Report of Scotland ') that in the year 1725-6 the few potato 

 plants then existing in gardens about Edinburgh were left in the game 

 spot of ground from year to year, as recommended by Evelyn : 

 tubers were perhaps removed for use in the autumn, and the parent 

 plants were well covered with litter, to save them from the winter's 

 frost. 



Though the plant may be propagated both by its seed and tubers, 

 practical management has confined the cultivation to the latter mode, 

 except for the purpose of raising new varieties or renewing old ones. 

 Those who are curious about varieties (which are now innumerable), 

 can almost indefinitely pursue their object ; for the seed of a species, 

 the red apple for example, will sport, and this too without hybridising 

 (that is, without the admixture of ita seed with that of any other 

 species, the produce of which would be hybrids^, into numberless 

 varieties of form and colour round, flat, oblong, red, pink, black, 

 white, mixed, and purple, of every shade and colour. These, wheth. r 

 hybrids or not, are reproduced through successive seasons bv the 

 tubers alone, if they possess those qualities which render them desirable 

 for continued cultivation, on account of peculiar adaptation to early or 

 late seasons, size, predominance of farina, Ac.* 



This mode of propagation by tubers either improves those qualities, 

 or gradually developes objectionable properties. Some varieties are 

 therefore permanently established, while the culture of others is either 

 abandoned, or, if continued, it is known that those varieties revert in 

 the course of a few generations to the nature of their parent kind, and 

 therefore cease to constitute a variety. 



In the vegetable kingdom, hybrid plants have not the power of pro- 

 pagation by seed ; but they can be rendered reproductive by budding 

 and grafting, or by means of cuttings, slips, and tubers, and an original 

 stock comparatively worthless may be highly improved by such model 

 of multiplication. But when a farmer possesses two or three kinds of 

 decided excellence, he will act wisely by not encumbering his stores 

 with too many varieties, which always occasion trouble and confusion 

 in the field management. 



In order to obtain seed, properly so called, the potato-applf, when 

 perfectly ripe, should be dried, and then disengaged from its seed by 

 rubbing with the hand. The seed should be. preserved in a dry place, 

 in paper or cloth bags, until the beginning of March or middle of April, 

 when it may be sown in wooden boxes or earthen pans, with a covering 

 of less than half an inch of well pulverised earth. The vessels ought 

 then to be placed in hotbeds of mild heat, such as is suited to the 

 raising of half-hardy annuals. The plants, when an inch high, should 

 be pricked out into other vessels, and placed in a temperature some- 

 what lower than before, to inure them to the external air, to which 

 they should be exposed after frosts have ceased. These plants should 

 be put out in drills sixteen inches apart, and with the interval of six 

 inches between the plants in the rows. They will produce tubers in 

 the first year, and these may be planted in the following season in the, 

 ordinary way. 



For very early crops, such as those which the ash-leaved and walnut- 

 leaved kind* in particular yield, the most successful treatment was that 

 practised by the late Mr. Knight, president of the London Horticultural 

 Society, from the course of whoso practice we give the following 

 details of instruction : Drills may be formed in a warm and sheltered 

 ii (and in the direction of north and south) during any of tin- 

 winter months, two feet apart, and seven or eight inches deep. Stable 

 dung, half decomposed, should be laid in the drills and combined with 



M. SuTRCTPt, a dlitlnfruiMird and accurate French Fxpcrimcntaliit, i . 

 to In the Dictionnnlre d'Agriculture,' found that out of 800 Tarictien It had 

 only one exactly like the original from which they wore raised ; and out o! thii 

 Ideal number be only found time worth perpetuating. 



