588 O T P O T collector many a heartache. M. Koprowski has of lato come to his solace by devoting a volume to their history. Stamp -collecting has for some years past possessed a literature large enough to till a respectable bookcase ; it bids fair ere long to need a large library for its storage. Of Russian stamps, general and local together, the total number of types exceeded 135 up to the year 1875. The table (XXV.) which follows will give the reader the chrono logical sequence of postage-stamps in all parts of the world. Year. : 1840 1S43 1S44 1845 Countries 184(3 1847 1843 1S49 1S50 1S51 United Kingdom. Zurich, Brazil. Geneva. Basel, StPetersburg(experimen- tal), Finland (envelopes), New York i (tentatively), St Louis. Rhode Island. United States, Mauritius (?). 2 Russia (envelopes). * France, Belgium, Bavaria, Vaud, Winterthur, Tuscany,-* New South Wales. Austrian empire, Italy, Prussia, Kfivnnv RpTilp^wic- - T-f nlstpin. Saxony, Schleswig-Hols S[>ain, Switzerland, Hanover, Baden (?), British Guiana (?), Victoria(?).s Year. 1852 1853 1854 1S55 1856 1857 1S5S Countries. Roman States, Parma, Modena, Brunswick, Thurn and Taxis post -district, Netherlands, Luxemburg, Isle of Reunion. Portugal, Cape of Good Hope, Tasmania. Norway, British India, Philip pines, West Australia. Sweden, Bremen, Cuba, Porto Rico, South Australia, New Zealand. St Helena, Natal. Naples, Poland, Moldavia, Nova Scotia, Buenos Ayres, Argentine, Peru. 9 Year. Countries. Year. Countries. 1859 Sicily, Romagna, Hamburg, St 1866 Servia, Honduras, Virgin Lucia, Bahamas, New Gran Islands, Shanghai, Kashmir, ada, Venezuela. Deccan, Sarawak. I860 Poland, Malta, Jamaica, Prince 1867 Heligoland, St Salvador, Guad Ed wardlsland, Dutch West In alajara, Bolivia, Malacca, dies, Liberia, New Caledonia. South African Republic. 1861 Greece, Bergedorf, British Col- , 1868 Azores, Madeira, Orange River, umbia, St Vincent, Nevis, Fernando Po. Sierra Leone, Queensland. 1869 Gambia, St Thomas, Angola. 1862 Roumania, Livonia, San Do 1S70 St Christopher, Paraguay. mingo, Antigua, Nicaragua, 1871 Guatemala, Japan. Costa Rica, United States of 1872 Portuguese Indies, Persia, Fiji. Colombia. 1873 Iceland, Dutch Guiana, Cura- 1863 Turkey, Turk s Islands. coa, Cabul. 1S64 Mecklenburg - Strelitz, Dutch 1874 Montenegro, Dominica, Lagos East Indies. (Gold Coast). 1865 Vancouver, Bermuda, Egypt. 1 " 1875 Punjab. The extent of the commercial traffic which has so rapidly grown Stamp- out of the increasing taste for collecting postage stamps is marked collect- ( sufficiently for our purposes) by a record of three facts: (1) the m a. aggregate number of manuals, periodicals, and current catalogues relating thereto, in English, French, and German alone, exceeds seventy ; (2) for a collection of postage stamps, made by Sir Daniel Cooper (of Australia) between 1862 and 1878, 3000 sterling was given in the last-named year by M. Philippe de Ferrari ; (3) the Galliera collection at Paris is said, upon credible authority, to have cost, up to 1883, in acquisition and arrangement together no less a sum than 57,600 (1, 440,000 francs). Next to these two collections ranks that of M. A. de Rothschild. 11 (E. ED.) POTASSIUM METALS. Under this heading we treat of potassium, rubidium, and caesium; SODIUM and LITHIUM, being less closely allied to potassium, have special articles devoted to them. Potassium. The three metals under consideration are all very widely diffused throughout nature ; but only potassium is at all abundant, and therefore we begin with it. The richest natural store is in the ocean, which, according to Roguslawski s calculation (in his Oceanographie) of its total volume and the present writer s analysis of sea water, contains potassium equal to 1 141 times 10 12 tons of sulph ate, K. 2 S0 4 . This inexhaustible store, however, is not much drawn upon at present ; the " salt-gardens " on the coast of France have lost their industrial importance as potash-pro ducers, if not otherwise, since the rich deposits at Stassfurt in Germany have come to be so largely worked. These deposits, in addition to common salt, include the following minerals: sylvine, KC1 ; carnallite, KCl.MgCl 2 + 6H 2 O (transparent deliquescent crystals, often red with diffused oxide of iron); kainite, K 2 S0 4 .MgS0 4 .MgCl 2 + 6H 2 O (hard crystalline masses, permanent in the air) ; kieserite (a hydrated sulphate of magnesia which is only very slowly dissolved by water) ; besides boracite, anhydrite (CaSO 4 ), and other minor components lying outside the subject of this article. The potassium minerals named are not confined to Stassfurt ; far larger quantities of sylvine and kainite are met with in the salt-mines of Kalusz in the eastern Carpathian Mountains, but they have not yet come to be worked so extensively. The Stassfurt potassiferous minerals owe their industrial importance to their solu bility in water and consequent ready amenability to chemical operations. In point of absolute mass they are insignificant compared with the abundance and variety of potassiferous silicates, which occur everywhere in the earth s crust ; orthoclase (potash felspar) and potash mica may be quoted as prominent examples. Such potassiferous silicates 1 A provisional issue by the post-office prior to legislation. 2 According to Gray, 1852 ; according to Earle (Stamp -Collector s Mag., xi. 168 sq.), 1850. 3 Embossed arms, crown, and post-horns on a circular dish. 4 According to Gray, 1849 (Cat., 6th ed.) ; according to both Earle (Stamp-Collector s May., xi. 168) and A. de Rothschild (Hist, de la Poste, ii. 208), 1876. 5 According to De Rothschild (ib., 215), 1851. Rothschild s date is 1852 (p. 218). 7 By Sir Bartle Frere. 8 Both Gray and Rothschild date 1859. Earle (ut supra] describes a Lubeck stamp of 1847. 9 Rothschild s date is 1857. are found in almost all rocks, if not as normal at least as subsidiary components ; and their disintegration furnishes, directly or indirectly, the soluble potassium salts which are found in all fertile soils. These salts are sucked up by the roots of plants, and by taking part in the process of nutrition are partly converted into oxalate, tartrate, and other organic salts, which, when the plants are burned, assume the form of carbonate, K 2 C0 3 . It is a remarkable fact that, although in a given soil the soda may pre dominate largely over the potash salts, the plants growing in the soil take up the latter by preference : in the ashes of most land plants the potash (calculated as K 9 O) forms upwards of 90 per cent, of the total alkali (K 2 or Na 2 0). 12 The proposition holds, in its general sense, for sea plants likewise. In ocean water the ratio of soda (Na 2 O) to potash (K 2 O) is 100 : 3 23 (Dittmar) ; in kelp it is, on the average, 100 : 5 26 (Richardson). Ashes particularly rich in potash are those of burning nettles, wormwood (Artemisia Absin thium), tansy (Tanacetum wUgare), fumitory (Fumaria officinalis), tobacco. In fact the ashes of herbs generally are richer in potash than those of the trunks and branches of trees ; yet, for obvious reasons, the latter are of greater industrial importance as sources of carbonate of potash. Carbonate of Potash (K 2 C0 3 ) in former times used to be made exclusively from wood-ashes, and even now the industry survives in Canada, Russia, Hungary, and other countries, where wood is used as the general fuel. In some places for instance, in certain districts of Hungary wood is burned expressly for the purpose ; as a rule, how ever, the ashes produced in households form the raw material. The ashes are lixiviated with water, which dissolves all the carbonate of potash along with more or less of chloride, sulphate, and a little silicate, while the earthy phosphates and carbonates and other insoluble matters remain as a residue. The clarified solution is evaporated to dryness in iron basins and the residue cal cined to burn away particles of charcoal and half-burned organic matter. In former times this calcination used to be effected in iron pots, whence the name " potashes " was given to the product ; at present it is generally conducted in reverberatory furnaces on soles of cast-iron. The cal cined product goes into commerce as crude potashes. The 10 Gray (6th ed., p. 258). Both Rothschild and Earle give the date as 1866. u See Stamp-Collector s Magazine, 1878. la Compare the interesting paper by C. Bischoff in the Journ. f.
Pracl. Chem., vol. xlvii. p. 193(1849).