IB) 



POST-TERTIARY 



POTASSIUM 



in tin- thirteen (totes was only about seventy-five. 

 A conspectus of the remarkable progress in the 

 ensuing century i* MMlitd in the table below. 

 Outstanding event* in the history of the American 

 postal service have been the negotiation of a jiostal 

 treaty with Kngland (1S46); tin- btradtwttM of 

 postage-stamps ( 1847 ), of stamped envelopes ( 1862 ), 

 of the system of registering letters (1855); the 

 rtablMuneot of the free delivery system, and of 

 the travelling post office system ( 1863) ; the intro- 

 duction of tin- money order system (1864), of 

 postal cards (IH73), and, between the last two 

 date*, of stamped newspaper-wrappers, and of 

 envelopes Wring requests for the return of the 

 enclos.nl letter to the writer in case of non-delivery; 

 the formation of the Universal Postal t'nion ( 1873); 

 the issue of ' postal notes ' payable to bearer ( 1883); 

 and the establishment of a special delivery system 

 (1885), uiuler which letters bearing an extra ten- 

 cent stamp are delivered by special messengers 

 immediately on arrival at the post-office of destina- 

 tion. Later progress is found in the rapidly-growing 

 system of free rural delivery, and in the exten- 

 sion (1900) of domestic rates to the island posses- 

 sions. The jiostmaster-general in n member of the 

 cabinet, Under him about 100,000 persons are 

 employed, of whom some 60,000 are postmasters. 

 Most of these, except letter-carriers tind clerks, 

 are liable to be removed on the accession to federal 

 office of a new political party. The following table 

 shows the increase, during the first century of the 

 department's history, in offices, length of mail 

 mutes in miles, revenue, &e., with figures for 1898. 



Mite. BmntM. Eipntlltun. 



|H,M S--MI" 



280.804 W.'.Kl 



62,386 4< -> 



1,111.927 1 



1,860,683 1,0 



1790.. 

 1800 

 1810. 

 MO 



1830 



75 



. 90S 

 tSOO 



. 4,500 

 8,450 



1840 ........ 13.468 



1860 ...... 18.417 



I860 ........ 28,498 



1870 ....... 28,492 



1880 ........ 42,1(89 



18W> ........ 62,401 



1898 ........ 73,670 



1876 

 20,817 

 36,406 

 72,4:l 

 115,176 

 166,730 

 178,67* 

 240,964 

 281,23 

 343.883 

 427,990 

 480,4l 



4.643,622 4 



6,552,971 6,21'J.UVI 



8.618,067 19,170.610 



19,772,221 2S,998,8S7 



S3.:ll.'.,47 *' 



60,882,097 8,30,717 



8,012,i.|!> WS.083,524 



As will lie seen, the United States post-office 

 department, unlike thai in (Ireat Britain, is carried 

 on at a loss ; this is due to the large amount ol 

 postal matter of certain classes carried at less than 

 the cost of distribution, and to some kinds of cor- 

 respondence carried free. In Isus there were 

 12,225, 70bY0 pieces of mail handled, \:>,4\ti.-*M 

 registered packages, 1,001,416 through registered 

 pouches, &c. In 1890 there were conveyed by jiost : 

 Letter*, pott-card*, Ac. ....................... 2,280.950,015 



Newspapers. Ac ............................... 778,428.616 



other article* ................................ 619.247.1W 



Article* wnt free of postage .................. 876,609,1(1.'. 



Art irl'-. .full kindi for foreign countries ...... 41,273,312 



Granil total ........ 4,006,406,200 



The number of post-offices in the United States 

 is larger than in any other country : but as regards 

 the number of persons employed the United States 

 takes third rank. It provides a post-office for 

 every 1003 persons, while in Great Britain the 

 proportion is one to every 2105 persons. 



See the article* STAMPS, TKLROBAPH. Tho following 

 work* may also be consulted : Poctmarter-freneral'i 

 Annual Keporta, iatncd yearly since 1865 ; Her Majeilu'i 

 Mail*, by Lewini ; Life of .Sir Rowland Hill : The Hit 

 of Penny Piatmje, by Sir K. Hill and O. B. Hil 



) ; Fifty Yean of Public Worthy Sir Henry Cole 

 < 1KK4 ) ; The History of the Port-office to 1836, by H. 

 Joyce (1893); t'ortu Yean at the Port-office, by F. K. 

 Bain ( 1896) ; Tkr Royal Mail (1885), and The Port in 

 fjrnnt and Farm (IKSKi), by the present writer. 



Post-Tertiary. See QUATERNARY. 

 I'OHJ. See HIM.. 

 Potash. See POTASSIUM. 



Potash Water. See AERATED WATERS. 



Potassium (sym. K, equiv. 39) is one of the 

 alkaline metAls. The letter K is selected as it* 

 symlrnl, as being the first letter of Kali, the Arabic 

 word for potash, the letter P being already taken 

 us the symbol for phosphorus. The following are 

 he chief characters of this metal. It is of a bluish- 

 whit* colour, and present* a strong metallic lustre. 

 It melto at 1 46-5'' (62 -5 C.), and at a red heat i- 

 converted into vapour. Its affinity for oxygen ia 

 so great that on exixisure to moist air it imme- 

 diately becomes covered with a film of oxide, anil 

 lience'it must lie kept below the surface of naphtha., 

 \Vhen heated it burns with a violet flame. Its 

 intense affinity for oNjgen is veil shown by tb- 

 in;; it into water, on which, from its low specific 

 gravity, '865, it floats. The metal ihrtnMti 

 oxygen from the water, and forms oxide of jMitii-- 

 shim (potash); while the liberated hydro-en 

 carries off a small portion of the volatilised (iotas- 

 sinm, and, taking fire from the heat evolved by the 

 energetic chemical action, bums with a brilliant 

 violet flame. The experiment is a very betntifa] 

 one, the burning metal swimming aliout rapidly on 

 the water, ami finally disappearing with an explo- 

 sion of steam, when the globule of melted potash 

 becomes sufficiently cool to come in contact with 

 the water. 



Potassium does not oecnr in the native state, and 

 can only be obtained by the reduction of its oxide, 

 potash. In 1807 I >ax y" prepared it by decomposing 

 its hydrated oxide ( potash ) by means of a voltaic 

 current, but this process is not applicable on the 

 large scale. It is now usually manufactured by 

 distilling a mixture of carbonate of potash and 

 charcoal in an iron retort. 



If proper proportions are taken, the mixture ia 

 wholly converted into carlionic oxide and potas- 

 sium, a- is shown in the equation : 



Carbonate of Potash. Carbonic Oxide. 



K,CO, + 2C = K, + SCO. 



Potassium forms two compounds with oxygen, 

 vix. a protoxide, K ? O, which constitutes potash, 

 and is strongly basic, and a peroxide. K a O 4 . Of 

 these the former is the only important one. 



J'utush can lie procured in the anhydrous form 

 by heating thin slices of the metal in air perfectly 



free fro misture or carlMinic acid. It is white, 



very deliquescent, and caustic. When moistened 

 with water it becomes incandescent, and the water 

 cannot lie expelled by any degree of heat. A far 

 more important substance is the II inlnili of 1'oiash 

 or C,iiintif 7VW, (KOH = K s < >)!,(> ). This is 

 commonly prepared by dissolving cailionate of 

 potash in ten times its weight of water, and gradu- 

 ally adding to the liiling solution a quantity of 

 slaked lime, equal in weight to half the carbonate 

 of potash used. The resulting compounds are car- 

 bonate of lime, which falls as a precipitate, and 

 hydrate of potash, which remains in solution ; the 

 changes being expressed by the equation : 



Carbonate of H1 . fc(-1 Carbonate of 1 1 yd rated 

 Potash. Potash. 

 K.CO, + CaOH.O = CaCO, + 2KOH, 

 The clear supernatant fluid is removed by dccanta- 

 tion, or by means of a siphon, into a clean silver 

 or iron basin, and is rapidly eva|>orated till it Hows 

 tranquilly like oil; it is then either cast into 

 cylinders in metallic moulds, or is |iourcd upon a 

 cold slab, and solidities on cooling. A- so obtained 

 it is very impure, but by solution in alcohol and 

 evaporation a very pure article 1 is prodii I. 



Hydrated potash, on solidifying after fusion, 

 occurs as a hard, grayish-white, opaque Imdy, with 

 a crystalline fracture', which may be readily again 

 iiiscd into a colourless oily fluid, but which only 



