analogous In hydrochloric a i Mil : 1 hey are 1 1 1 i Uet let ! by pressure and col< 1, 

 thev fuiiif in the air. fiirm Solutions and hydrates of con-taut boiling 

 point, and react on nu'tal.s, oxides and salts. A-C. <S ( )nlv the relatiyely 

 casv decompo-abihty of hydrobromic acid, and especially of hydriodic 

 aciil. clearly distinguish the-e acids from hydrochloric acid. For this 

 rea-on. hydriodic acid acts in a number of cases as a deoxidiser or 

 reduce]', and frequently e\vn sei'yes as a means for the transmission of 

 hydrogen. Thus I'ertheloT. Ha ever. \Vreden.and others, by heating 

 unsaturated hydrocarbons in a -olution of hydriodic acid, obtained their 

 compounds with hydrogen nearer to the limit (' II ., or even the 

 -aturated compounds. For example, ben/ene. <,!!,. \\hen heatr-d in a 

 cli.-e t l tube \vith ; -tronu' -oluiion of h\dri"dic acid, n'iyes he.xylene, 

 (' ,11, . The easy decomposability of hydriodic a<-id accounts for the 

 fact that iodine due- not act 1 >y metalepsis on h \-drocarbons, for the 

 li\ . ! ro^'ei i iiiilule libei'atetl \\iih the product of metalepsis. |JI. formed, 

 ^i\-es iodine and the ii\-dro^-en compound. RH.baek auain. And there- 

 fore, to obtain t he products of iodine substitution, eit her iodic acid. 1 1 1( )., 

 ( Kekult'). or mercury oxide, Hijf< ) ("\Ves.e]sky), is added, as the\'imme- 

 diately react on the liydro-vn iodide, thus : II |< >, + 5II I =.>H,< > + .^I,. 

 in-. 1 lu ( L'l I I = I li:! +H.,<>. From these consideration- it will be 

 readily understood that iodine acts like chlorine (or bromine) on am 

 lu oni a and sodium hydroxide, for in this case the hydriodic acid produced 

 fonn- N 1 1 , 1 and Na I . Thus with t i net lire of iodine, or even the solid 

 * . en!, a -olntion ''i ammonia immediately forms a lii^ldv-oxplo^ive 



that IV, i ' ' M'i" ' ' ' lift wren tin- lt\ ilriciilic acid 



. i ,, I.IMI.I- I'M ,1 and I'l . Miv InnniMl. 



' ' ' ;|H. ivacti,,!! IH t\V.MMI | -1 1 ,- 1 .1 i . .1' 1 1- all ! iixlilli- alld ttnt.T 



.1 '. ... \ l >' ' Hi |,n.c.-i-U ,[uici!\. l.iii iii-v,Ttlir!->- n-cjuiri- 



1 he I'racl ion prncrciU \\ itlmllt t lie 



linn I 1 M I II .( ) IMI-O, .Mil. 



I' Wiitrr arr place, 1 in a LVtiii-l. and a 



' . I . \ ' : 1 ! 1 1 a 1 t i r - : 



