arid, barium chloride, I'aCl.,. i- obtained in solution, and the sulphur is 

 disengaged as gaseous snip] in ret ted hydrogen, Ba8 + -HC1= 15alM v -f H.,S. 



In tins manner barium sulphate is converted into barium chloride,' 1 ''* 

 and tin- latter by double decomposition with strong nitric acid or nitre 

 o;ives the less soluMe l>arium nitr.-ite, T>a( X( ).,).,.'' or with sodium 



-' i ' pliulc. The hydro_;i-ii sulphide is sometimes removed from the solution by boiling 

 with the oxides of copper or /.hie-. Ifsuirarbe added to a solution of l.ariiun sulphide, 

 then on heating barium saccharate is precipitated : it i- decomposed liy carbonic anhy- 

 dride, so that liarium carbonate i- I'ornied. An ei|nivalent mixture of sodium sulphate 

 ui;h barium or strontium sulphates when ignited with charcoal Drives a mixture of 

 -odium sulphide and bariui tiuin sul])hide. and if this mixture be di-solved in 



water and the solution evaporated, then barium or strontium hydroxide crystallises out 

 on cooling, and sodium hydrosulphide, NallS. is obtained in solution. The hydroxides 

 I la 11 .< I . and Sri I., O., are prepared on u lar-e scale, bein^ applied to many reactions ; for 

 example, strontium hydroxide i- pi-epared for sUi, r ar works for extract in:.' crystallisable 

 -ii'j'ar fri on UK ila ssi -. 



We ma\' remark' that 1 '>oii-sin c _:'ault . by iu'nit inu' barium sulphate in h\ drochloric acid 

 _,i-. obtained a complete decomposition, with the formation of liarium chloride. Attention 

 -hould also be turned to the fact that (Irouven by lieatinjjf a mixture of charcoal and 

 strontium -ulphate with maLnie-ium and potassium sulphates sho\vt-d the easy decom- 

 posability depending on the formation ,,f double salts, such as SrS.K ,S. \\ hich are easily 

 -olnble in water, and j^ive a precipitate of strontium carlionate with carbonic- anhydride. 

 In such examples as these we see that the force which binds double salts may play a part 

 i directing the course of react ion-, and the number of double salt- of silica on the earth's 

 -nrface shows that nature take- advantage of these force- 'n her chemical processes. 



manner: finely-ground barium sulphate is heated with coal and manganese chloride, 

 forming the residue from the manufacture of chlorine. The mass becomes senii-liijuid, 

 and when it evolves carbonic oxide the healing is -topped. The following double decom- 

 po-Mtions proceed durini: this operation : lir-t the carbon takes up the oxygen from the 

 I- irium sulphate, and -he- sulphide. BaS, which enters into double decomposition with 

 the chloride of manganese. MnCl ,. forming manganese sulphide. ]\1 nS, which is insoluble 

 ,.,'ter. and -olnMe barium chloride. This solution is easily obtained pure because 

 many !'oi''' : _ n impurities, -uch a- iron, remain in the insolnl.le port ion with the manganese. 

 The suhiti < III ride obtained in thi- manner i- chielly used for the prepara- 



tinii of liarium -idpliate. which is pi'ecipit ated by sulphuric acid, liy which means Imi-iinn 

 * ,i 1 ,,1,'it r \~ re formed a- a po\\der. 'I'll is salt i- chai'actei'ised b\- the fact thai it is unacted 

 ,,n b\ thei ' nl chemical iva;_-ent -. is insoluble in water, and i- not dissolved by 



cid-. but is -!'/i tl\ - led . icon- -olulion by the prolonged action of alkalis 



,1 boili )!_'. the sohtl ion -i\ es liarinm eai'bonaie. Chapter \.l. OWI'IILT to this, artificial 

 barium siilpha.te form- a p. nn, HP-!!' uhite painl \vhich i- il-.-d instead of white lead. 



; , uhite i|n. ' I ' '!< ' tile ill I io)l of Sll 1 ph U I'et t ed h \ d 1'o-e II , W 1 1 icll 



IT, v ; ife ; . i.l. Heue, it I I.. , i i, rmed ' I.I inc lixc ' or permanenl white.' 



The -olntion ot ,,ne part of caleium chloi-ide al I'll requires !:;<; parts of water, the 



p.Tature. and the ,,],;,,:, ,,| I ,., ri n i n . 1 1 lo,-',|,. L"ss; ] .arts of water. The .olnbihf y of the 



;oi-m Iia('l ,.iiU .( > and Sr< '! ..I'd 1 ,( ) l!a latter resembles the salts of calcium and 111:1^.' 



'i 'I i ..-'<< ' M ive a cr\ lallo hydrate containing 



1 | ! ( i . ,. . M I ;,, '.' i . i \ i | -i! ': ater thai llie\ i-| ia rate in rat lie|- 



