300 Scientific Intelligence. 



used in the experiment. Two modes of stating the results are 

 proposed: 1st. that the quantity of the new body formed in an 

 intiniteh -i, .r tim. - pi -p. riona] to i he c> . ntrati m // at that 

 time; or 2d, that this quantity is proportional to the number of 

 molecules „f the liquid which act upon a unit of surface of the 

 solid. Taking the reaction bet* .-;<• acid, and 



assuming that a unit, of zinc surface dips in a unit of volume of 

 the acid, the first hypothesis is expressed by the differentia! equa- 

 tion d[E 2 ]=kydt," m which d[H 2 ] expresses the quantity of 

 hvdi Li'en set frei in th infinit ly sn ' ii ue dt, and k is the pro- 

 portional coefficient. Since 49 parts of H ,Si > are required to 

 evolve 1 part of H, we have [H 2 ]=-^[H s SO_ 4 ]=-^- Dif - 

 Bg, dfH t ]=— -fady. Equating with this the above ex- 

 pression for d[B 2 ], we have — = - 49kdt. By integration be- 

 tween the limits y t and y , the value of y t can be obtained ; and 

 by substituting this value for >/ in the first equation given above, 



/»[H,1 *t ... 



J d[E 2 ]z=ky / e~^ U dt, there is obtained [H 2 ]= ¥ V2/o 



(l-e-& kt )= T \(y Q -y ( ), from which fc=I.I."l comm. log. ~. 

 The experimental results with zinc and sulph n > id n b :_ 

 uniform. !!!<• author t.M k Carrara marble and hydroch 

 the marble parallelopipeds being accurately measured. !; r «m 

 this the Burface-area so the volume of liquid 



required to give a unit of volume to each unit of marble surface. 

 The concentration of the acid was determined \, : , 

 giving y . The carefully weighed marble was placed in the acid 

 for a known time, then removed, washed, dried and weighed; 

 from the loss, the carbonic dioxide evolved and the acid consumed 

 were determined, giving y t . From these data, by the formula 

 *==££ AM log -^ , the value of ffifcM, and consequently of A, was 

 calculi ted Aa a mean of 53 well agreeing experiments, the 

 value of --*AM was found to be D-oiTOo. and of/ n-i.JU± >'' " -« r 

 20° and 760 mm. Since this value is constant, it follow 

 first supposition represents a fact, and that the quantity of carbon 

 • in a definite moment" of time ^ 

 directly proportional to the concentration of the acid at that 

 Kajander, Boguski has now ox- 

 ;her acids, using nitric and hydro- 

 e\p, laments The\ find tie \alue- \\ ' '■' ;l1 " 1 



"" id 0-0185, being sensibly the same as 



■ .,- these 'three acid- is 



proportional to their molecular 



.?[CO a ] = 



_ =kydt, we have the velocity^ of the reaction 

 9ts ~\tt ' — k y- Consequently when different acids of the same 



