EXPERIMENT STATION BULLETINS. 



833 



all the acids employed in this investigation, which included only HCl, 

 HNO3, HoSO^, and H.,C„04, gave the usual acid cuiTe upon being titrated 

 with Ca(0H)2, NaOH, and KOH; the NH^OIH, however, failed to give 

 the characteristic acid curve, at least in any pronounced form. 



Besides the factor of dissociation, there is still a second factor which 

 might produce the acid curve, and that is the insolubility of the product 

 formed from the reaction between the acid and the base. Thus, for 

 instance, take the case of CaH4(P04), and H0C0O4. Upon the addition of 

 Ca(OH), the Ca combines with CaH,(POJ, aiid'HoC.O, to form Ca.lPO,) 

 and CaCo04 which are quite insoluble. As long, therefore, as the reaction 

 is not completed the depression will diminish with the increased addition 

 of Ca(OH)o but as soon as sufficient Ca(0H)2 has been added to com- 



Figure 4. Curve showing the almost immediate rise iu the depression of alkaline 



soils upon adding Ca(OH)2 



plete the reaction, then there will occur a minimum depression; beyond 

 this point the depression Avill commence to rise with further addition of 

 Ca(0H)2. 



The question already raised, therefore, namely, may not substances 

 other than acids and acid salts react with Ca(OH). to produce a curve 

 similar to the acid curve, can now be answered. . It should be declared at 

 once, however, that while this might be so Avith certain compounds, yet 

 a large number of compounds have been employed for the purpose of test- 

 ing out this point and in no case was there an acid curve obtained. 



On the other hand it has been found that certain compounds v/hich are 

 neither acids nor bases may react between themselves to form other com- 

 pounds and thus yield a curve similar to the acid curve. A most strik- 

 ing case of this kind may be cited the reaction between BaCl., and 

 AgoS04. If AgoSO^ is treated with BaCl, the freezing point depression 

 decreases similarly to that when HCl is titrated with Ca(0H)2 until 

 the reaction is com])lete where a minimum depression is registered and 

 then the depression commences to rise with further addition of BaCl^^. 

 105 



