i\ 



K t 8 (potassium milphido), which in disn!pated in smoke. 

 Those products of the combustion occupy, at t rnpora- 



turo of tho oxplouion, about 1,400 tim 

 powder. 



^fulminant is a mixture of 3 parts of nitre, 2 potamiium 

 carbonate, and 1 Bulphur, \\liich, when heated on an iron Bhovol 

 until fuaion takes place, explodes violently. 



a other Bolts which potash makes with every acid Potas- 

 sium I'lili'i-titi- (K('lO 8 )iH tho most important. It is procured 

 by Hubtnittiiig a mixture of potaHsium carbonate and uluked 

 lime, inoistenod, to tho action of chlorine gas ; tho chlorate 

 formed is separated by lixiviation and crystallisation. 



.-ii combines with tho halogens and sulphur, when 

 heated with them, forming many salts of great medicinal 

 value. 



All the salts of potassium, if introduced on a platinum wire 

 into tho redui'ltiy flame of tho blowpipe, impart to tho flamo a 

 purple tiii'.rc: and with bichloride of platinum, a concentrated 

 solution containing potash gives a yellow precipitate. 



SODIUM. 

 SYMBOL, Na COMBINING WEIGHT, 23 SPECIFIC GRAVITY, 0'97 



MELTING POINT, 98. 



Tho discovery of sodium was immediate upon that of potassium. 

 The metal is obtained from sodium carbonate by an analogous 

 method to that which produces potassium ; it distils over with 

 carbonic oxide, with which, unlike potassium, it does not 

 combine. 



Sodium is now prepared in largo quantities, for it is used in 

 the extrication of magnesium and aluminum from their salts. 

 When thrown on water it decomposes it, but the action, unless 

 the water bo thickened by starch paste, is not sufficiently 

 violent to ignite the escaping hydrogen. 



Its compounds are widely distributed in Nature. Indeed, 

 the " spectrum analysis " would indicate that the presence of 

 sodium, in some form, is all but universal. The sea is its great 

 repository, its waters containing 3 per cent, of sodium chloride, 

 or common salt. 



Tin' (hide of Sodium, or "caustic " soda (Na 2 0), may bo pro- 

 cured in a manner analogous to that which gave potash, and 

 the same is the case with the hydrate that is, by tho action 

 of milk of lime on carbonate of soda. 



Sodium Nitrate (NaNO ? ), or Chili Saltpetre, is found in that 

 country in large quantities. Indeed, tho natives of Chili aud 

 Peru build their houses of blocks of tho salt. It cannot be 

 used in the manufacture of gunpowder, for it is deliquescent ; 

 however, it is of indirect use, for nitre may be made from it. 



Sodium. Chloride (NaCl) may be procured from tho sea by 

 evaporation, but is generally supplied by salt mines, the prin- 

 cipal of which are in Cheshire, Poland, and Spain. The Polish 

 mine of Wieliczka is a mass of salt 500 miles in length, 20 

 in breadth, and at least 1,200 feet thick, a quantity suffi- 

 cient to supply the culinary demands of the world for ages. 

 Salt when crystallised is rock salt, or sal gem; the crystals 

 are cubic. 



Sodium Sulphate (Na 2 S0 4 + 10 H 2 O), or Glauber Salt, is re- 

 markably efflorescent; that is, it gives off its water and 

 crumbles to powder. It has a saline bitter taste, and is used 

 as a medicinal purgative. 



Its preparation will be referred to in the making of 



Sodium Carbonate (Na 4 OCO a ), which constitutes the most 

 important of chemical manufactures. It is used in the manu- 

 facture of glass and soap, in calico printing, in softening hard 

 waters, and in the preparation of all tho other salts of soda. 



Formerly it was procured, as potash is still, from the ash of 

 certain plants, but this has been superseded by its manu- 

 facture from the chloride. 



The process consists of two stages : 



1. The Salt-caJce Process. A charge of five or six cwt. of 

 salt is thrown into a shallow cast-iron pan, about 9 feet in 

 diameter, and 12 inches deep at the centre. Tho lid of this 

 pan has two openings ; through one an equal weight of sul- 

 phuric acid is introduced. The following reaction occurs when 

 heat is applied : 



H,SO. + NaCl = HNaSO, + HC1. 



The hydrosodio sulphate remains, and the hydrochloric acid 

 passes through the other opening to the bottom of a vertical 

 flue, which is packed with pieces of coke, over which water is 



allowed constantly to trickle ; thin water absorbs the gas, and is 

 the souroo of tho hydrochloric ; when the action 



becomes sluggish, tho hydrosodic >;ulphato is raked out and ex- 

 posed to a higher heat in :. - of brick- work, the fluo 

 from which also vcrti--:il flu.-. Jjy this means tho 

 atom of hydrogen which is associated with the sodio salt is 

 driven off, thus 



HNuSO 4 + NaCl = Na.SO. + HCL 



This sodium Bulphato which in the result of this process is 

 known as salt-calif . 



2. Soda-ash Process. The Bait-cake is ground up with an 

 equal weight of chalk (CaOCO.) and half its weight of coal. 

 Tho mixture is then submitted to tho heat of a " roverberatory ' 

 furnace that is, it is spread on a hearth, over which the flam* 

 of the furnace passes. The mixture melts, and these two reao 

 tiona take place : 



1. Na,SO. +40 = Na,8 + 4CO. 



2. Na,S + CaOCO, = Na.OCO, + CaS. 



The calcium sulphide and the other impurities being insoluble, 

 the sodium carbonate, or soda-ash, is washed out. Soda 

 crystals, used in washing, are got by saturating a solution with 

 soda-ash, and allowing it to crystallise. 



The Bicarbonate of Soda, which is used in effervescing drinks, 



ia H f OCOj, and is made by exposing soda crystals to the 

 action of carbonic acid. 



Sodium Hyposulphide (Na 2 OH s OS 1 O 2 + 4H 2 0) has tho power 

 of dissolving some silver salts ; hence its employment in photo- 

 graphy. Sodium is an element of these salts : 



Sodium phosphate = Na,HPO + 12H,O. 

 Microcosmic Salt = NaNH.HPO,. 

 Borax = Na a B 4 O, + 10H a O. 



The other sodium salts are of less importance. 



LITHIUM. 



SYMBOL, Li. COMBINING WEIGHT, 7 SPECIFIC GRAVITY, 0'59 

 MELTING POINT, 180. 



Lithium is the lightest of the metals. The spectrum analysis 

 declares it is widely distributed. By this means it has been 

 detected in most waters, in milk, and in tobacco. Lithium 

 chloride imparts to flame a brilliant crimson tinge. Tho metal 

 itself is obtained by decomposing this salt by means of the 

 galvanic current. 



Lithia (Li 2 O) stands between tho alkalies and the alkaline 

 earths. 



AMMONIUM (NH 4 ) has been noticed. 



RUIIDIUM and CAESIUM owe their discovery to the spectrum 

 analysis. Eubidium takes its name from tho red line its 

 compounds form in the spectrum. Cfcsinm gives two blue 

 lines. These metals closely resemble potassium. Their salts 

 are widely distributed, but in very small quantities. As yet 

 they have no commercial and but little chemical interest. 



LESSONS IN GREEK. XVI. 



COMPABISON OP ADJECTIVES. 



SUPERLATIVE (from super, above, beyond, and latus, carried) is 

 in grammar applied to adjectives when they are in that form 

 which signifies the greatest degree or amount of tho quality 

 described by them. The degree below, or an inferior degree of 

 the quality, is called the comparative; and the simple state 

 of the adjective is named the positive: for example, street is 

 the positive, s\ceet-er the comparative, and sweet-est the super- 

 lative. 



The Greek language has two forms of comparison. The first, 

 and by far the most common, adds to the positive -repus, -rtpd, 

 -rtpov for tho comparative, and -raros, -rarrj, -rarov for the super- 

 lative ; tho second adds for the comparative -luv, -lay, cr -oif, -or, 

 and for the superlative -IOTOJ, -nrrij, -urrov. Tho terminations 

 -or, -d, -ov, etc., respectively point out the masculine, the femi- 

 nine, and the neuter gender. 



As in Latin and English, the superlative in Greek denotes 

 either the highest degree of a quality, or a very high degree. 



Instead of these ordinary forms tho comparative may be 

 indicated by /j.a\\ov, more, and the superlative by ftaAtora, inosty 

 put before the adjective. 



