TUANSACTIONS OF SECTION B. 



671 



aciils, pnntaininp: iieitlier tiinirstic, nor molyhdic nxido, as for instanco, r2\'.,0. . 

 p„(). . .'jHiiO + 4") mi., ami l^OV.O. . r/l . (ill/) + ;j;J aq. Thest> compound's fii; 

 tKvmed pliospbo-vanadate.s; ar.^'enico- vanadates also occur as "well us various series 

 contiiiuinar vanadic dioxide, as well as pentoxide — a particular case beiiitr for 

 iustance, 18VJ)- . \(X, . -JV.O-, . 7(N1I,),0 + oO aq. lu conclusion the author 

 gliowcJ that the numerous compounds of tlie type, PCI- . SbCl-, long- known to 

 clicinists, in many cases at least corresponded to very simple forms of complex 

 acids. 



2. On an T^.vrihiple of Chemical EqviUhrhn)}. 

 Bi/ A. Vkuxox llAKCo'uitT, M.A., LLJJ., FM.S. 



;"!. On the Iiu-omplete Comhustloii of Gases. By H. I>. Dixox, ^LA. 



(1) Bunsen's orig-inal expei'iments on the incomplete comhustion of mixtures of 

 ravbonic oxide and hydrogen are vitiated by 1 lie presence of aquiH)us vapour in 

 the eudiometer. JJoth llorstmann's ex])eriments and my own show that no altera- 

 tion pc)' f^id/iint occurs in tlie ratio of thi: ])roducts ol'cf)nihustion. 



(L') A mixture of dry carbonic oxide and oxygen does not explode wlien an 

 electric spark is passed throuirh it. Tlie union of carbonic oxide and oxy^-en is 

 fllffcted indirectly by steam. A mens trace of steam rende.s a luixtui'o of oxygen 

 and carbonic oxide explosive, 'i'iie sleiim lUidergoes a srries of alternate reductions 

 and oxidations, acting as a 'carrier of oxygen ' to the carbonic ( xide. A\'itli a 

 verv small quantity of steam, the oxiilation of carbonic oxide takes ])lac(! slowly. 

 As the (piantity of steam is increased, the raj)idity of the exjilosion increases. 'J'he 

 mean rate of exjdosion for one metre was found to increase l'rom?(i metres a second 

 — wlien the mixture was passed over anhydrous phosphoric r.cid — to .'! 17 metres 

 per second, when tlie mixture was saturated with aqueous vapour at OO'' C. 



(;i) Wlien a mixture of dry carbonic oxide an<l liydrogen is exploded with a 

 quantity of oxygen insnilicicnt i'or complete conibustimi, llie rati.) of the carbonic 

 acid to the steam formeil depends upon the length of the column of gases .and 

 the pressure under whicli the gases are fired. By continually increasing the initial 

 pressure, a point is reached wliere no further incrtnise in tiie jiressure ailects the 

 products of the reaction. At and above this 'critical pressure" the result is in- 

 dependent of the length of tlie column of gases. The larger the proportion of 

 oxygen used, the lower the ' critical jiressuro ' is found to be, 



(1) When dry mixtures of carbonic oxygen and hydrogen in varying proportions 

 are ex])loded above tlit- 'critical ])ressure ' v.dth oxygen insufilcifiif for complete 

 combustion, an oquilibriura is established between two opposite chemical changes 

 represented by the equ.atious: — 



(!) (;o + ii,.o = co.. + ii,, 



(ii) (-'O, + ]"[, = CO + ILO 



so that at the etid of the reaction the product of the carbonic oxiile and steam 

 molecules is equal to the product of the carbonic acid and hydrogen molecules 

 muhiplied by a coellieient of allinity. This result agrees with llorstmann's con- 

 clusion. But Ilorstmaun considers the coidficicnt to vary with the relative mass of 

 oxygen taken. 



(■")) A small difference in the initial temperature at which the gases are fired, 

 makes a considerabh; dill'eroiici- in tli.- products of the reaction. This (lil!(>rence is 

 due to the condensation of steam by llu sides of the vesselduringthe explosion, and 

 its consequent removal from the sphere of action during the chemical changes. 

 When the gases are exploded at a temperature snillciently high to ])revent any con- 

 densation of steam during the iirogress fif th(> reaction tlie cotliieient is found to 

 be constant, whatever the quantity of oxygen used, provided tlie hydrogen is more 

 than double the oxygen. 



(G) The presence of an inert gas such ns nitrogen, by diminishing the intensity 

 of the reaction, favours Ihe formation of carbonic acid iu preference to steam. 



I 



