448 Dandeno — Relation of Mass Action to Toxicity. 



growth at about n/16, because sodic chloride, which is about 

 5/6 dissociated at this concentration, permits growth. The 

 sodium, in the case of JSIaCl, appears to be but slightly toxic. 

 Nor can the C0 3 ion be very toxic, from Table IV. Whence 

 then this great toxic action of Na 2 C0 3 ? Basing our views upon 

 the theory of electrolytic dissociation, it ought to be about the 

 same as NaCl or Na 2 S0 4 . But it is far more so. From this it 

 would seem that the theory was insufficient, or possibly erro- 

 neous. The explanation, in the writer's opinion, is that the 

 Na 2 C0 3 breaks up, in aqueous solutions, into Na 2 and C0 2 and 

 then reacts thus :— Na 2 C0 3 + H 2 = 2NaOH+C0 2 . It would 

 then be practically a solution of JNTaOH of a concentration iden- 

 tical with that of Na 2 C0 3 , which was chemically equivalent. 

 This is quite probable from these experiments. If this explana- 

 tion be correct, the theory of dissociation may give very 

 misleading notions as to the actual condition of affairs. 



The bicarbonate of soda affords another illustration. This 

 may dissociate into JS T a and HC0 3 , or into H and NaC0 8 , or 

 into Na,H, and C0 3 . The experiments show that the pea will 

 grow in 25 cc n/12S and in NaOH n/266. If the bicarbonate 

 dissociate according to the first plan,. the seedling ought to live 

 in a solution about n/S ; and if according to either of the latter, 

 in a solution of about ?i/2048. It, however, does neither. 



Pea seedlings will live in small quantities of the bicarbonate 

 at a strength of n/l§ and in similar quantities of NaOH at 

 w/128, but in chemically equivalent quantities there is just 

 half as much sodium in the bicarbonate as in the hydroxide. 

 They would compare then at about 4:1 in toxicity, the hydrox- 

 ide being the stronger. But since this substance may dissociate 

 in three ways at least, we may have a dissociation as follows, 

 with possibly an accompanying chemical action ; 8NaHC0 3 

 produces Na 2 + 2C0 2 + H 2 and 6Na and 6HC0 3 . This 

 might easily give a chemical reaction from Na 2 and H 2 of 

 2NaOH. Hence from 8 molecules we get 2 molecules of 

 NaOH or 2 OH ions. The ions Na 3 and HC0 3 are prob- 

 ably harmless, judging from Table IT. This is in the lan- 

 guage of the theory. These explanations throw some light 

 upon the alkaline reaction on litmus, and other indicators, of 

 the so-called acid salt NaHC0 3 . Theoretically it ought to 

 react acid, if an3^thing, but practically it reacts rather strongly 

 alkaline. 



Similarly also with Na 2 C0 3 . Theoretically it ought to be neu- 

 tral, but it actually reacts very strongly alkaline. The explana- 

 tion, therefore, is, that in the process of dissolving in water, 

 an actual chemical reaction takes place by some rearrange- 

 ment of the molecules, or groups of molecules, in the solu- 

 tion. The ionization theory does not aid at all, rather the 



