ITS PIMNCII'I.F.S OF CHK.MJSTKV 



heated above 4U , however, it decompt ises, forming chlorine, oxv^eiu 

 and perchloric acid : HK'H > ; , = L ( J1< '!<>.,+ 1 1 ,< ' + ('!, -f< > : .. When con- 

 siderably concentrated the acid acts as an exceedingly energetic oxi- 

 diser. so tliat organic substances, when brought into contact with it. 

 burst into llainc. Iodine, sulphurous acid, and similar substances 

 liable to oxidation form higher oxidation products and reduce the 

 chloric acid to hydrochloric acid. Hydrochloric acid gas gives chlorine 

 with chloric acid in the same manner as it acts on the lower acids : 



Hcio :{ + :>Jici=:m./> + :tt.'i,. 



l>y cautiotis]\- acting on potassium chlorate with sulphuric acid, the 

 dioAdi' (I'Mvr'u' / ro,.-i<!<>),C\( >,. :! '' is obtained (J)avy, Millon). This gas 

 is easily li-|tietied in a freezing mixture, and the liquid boils at +10 . 

 The vapour density (about '-\~> if 11 = 1) shows that t he molecule of this 

 substance is ( i< >.,.'" In a gaseous or liquid state it very easily explodes 

 (tor instance, at i)(>" 5 or by contact with organic compound.s or fineK" 

 divided substance.--. Are.), forming Cl., and ( ). and it therefore in many 

 instances. " acts as an oxidising agent, although (like nitric peroxide) 

 .it may be itself further oxidised. 1 '-' In dissolving in water or alkalis, 

 chloric peroxide gives chlorous and hvpochlorous acids 2C1( )., + 2KH( > 

 = K ('!<).,+ KC10, + H,O and therefore, like nitric ]ero.xide. the di- 

 oxide may lie regarded as an intermediate oxide netween the (unknown) 

 anhydrides of chlorous and chloric acids : H'H ., = O.,< ), + ('!.,< ).. 3 



" b IHM ;_<Ta.niH of -ulpliuric acid arc conlcd in a niixturr of ice and ^alt. and IT. 



grains of pou'dcrcd potassium chlorate ai'c gradually added to the acid, \vliicli is then 



cai'etully distil le<l al 'Ji i to }' ' . t lie \ a] n >u r L;'I \'en i ill' lieinjjf condensed in a t I'eexini,' mix t lire. 



]'ota>siuni perchlorate i- then t'ormed ; :;K(']O- -Jl I. S( ). - -Jl\" HS( >,-- K( '1O,- "2('\( ), 



II ( ). The reaction may result in an explosion, ('ah'crt and I hivies obtained chloric 



jieroxide \\itlimii tin- least danger liy heatinu: a mixture of oxalic acid and potassium 



chlorate in ;i test tube in a water-bath. In thi> case 1 2K( 'K >-, :!( '.,] I ,( ),'JH..( ) 



J( ' ,11 1\< i; 'JCO , 'J('K), si I ,( ). The reaction is still further facilitated by the addi- 



tion of a ~ni, ill <|iiantitv of sulphuric acid. 



'" llv analogy \\itli nitric peroxide it would lie expected that at low temperatures a 

 doubling of the molecule into ('!,<), would take place, as the reactions in which it 

 act-, as the mixed anhydride of H ('!<>, ami H <'!<>.-, point out. 



" Owin^r to the formation of this chlorine dioxide, a mixture of pota-siuin chlorate 



and sU^rar i - inflamed b\ a drop ol siilpimric add. 'I'ln- jiropertx' was formerly made 



11-1: ot for makiiiL' matches, and i- now sometimes employed for setting tire to explosive 



i i means of an arrangement in which the acid is caused to fall on the mixture 



e moment re.piired. An interestin (pi-riiin-iit on the combustion of phosphorus 



l,e conducted with chlorine dioxide. Pieces of phosphorus and ot 



(thron-h ., Ion- funnel : the phosphoric then I Minis at lli- ex pen -e of the chlorine di 1 ,xide. 

 i - I'ot.i ,iiiin permanganate oxidises chlorine dioxide into chloric acid (Fiirsti. 

 " The eiichl.irine obtaine<l b\ Davy b\ ^i-ntlv heat in. L r potassium chlorate with hy<lro- 



i ; 1'eliali a mixture of ,-hlorine dioxide and tree chh.rine. The li.piid and 



. o: .i- Note :;:,i. uhich Millon con idered t o ! ( '1 .()-. pr, .balily contains 



.1 mi vt lire oj ( |( ) , vapour del i sit \ :!."M, ( 'I ,O :i i who-,e \ apoiir density sliouhl le ."j'.h, and 



e lil, nine s a poui' 1 1 1 !;',! \ ',' t 'i'~i . because it \ apoiir den -it s wa -determined to be about III. 



