Mercuric Chloride by Phosphorous Acid. 359 



1 2a — 



a * 2{a)h x ~ 2(a)* 

 Substituting this value in equation (8) and setting k^7ca-^=k z 



J= *,(a -lx) (5- ix) (C + «), (9) 



which is the equation sought. 

 This may be written 



§ = J(9a-«)(8S-«)(0+«) > 



and, for convenience in integration, may be further simplified 



Jc 



by setting ~ = K ; 2a = A and 25 = B, gives : 



-^ = K(A - x) (B - ap) (C + a), (10) 



K = 



whence 



2-3 



. /A - x\ B+c I B \ A+C /C + a?V 



(A - B) (A + C) (B + C)« 



(11) 



If the amount of hydrochloric acid formed in the reactions 

 is small as compared with the initial concentration of hydro- 

 chloric acid used, — p — may be set equal to 1. Equation (10) 

 then assumes the form 



dx 



-j = K(A — x) (B — x), or 



K- 2 ' 3 lo g ( A -*> B (12) 



^~ (A-B)« g (B-«3)A l ; 



Experimental. Standardization of the Mercuric Chloride and 

 the Phosphorous Acid. 



The desired amount of mercuric chloride was dissolved in 

 distilled water or in aqueous hydrochloric acid of known con- 

 centration. Of this solution 10 cm3 were pipetted off, by means 

 of a carefully calibrated pipette, and transferred into several 

 glass test tubes of about 40 crn3 capacity which had previously 

 been constricted at about 1^- inches from the mouth to a size 

 just large enough to admit the stem of the pipette and to allow 

 the displaced air to escape. To this were added 10 cra3 of a 

 solution containing about \\ times the theoretical amount of 



