vin THE FORMATION OF IRREVERSIBLE SALTS 301 



The chlorides and acetates of the alkaline earths generally require 

 to be in much higher normal concentrations than do the corresponding 

 alkali salts ; reversely, the thiocyanite, iodide, and bromide of calcium, 

 precipitate in relatively low concentrations, while the corresponding 

 alkali salts do not precipitate at all. 



As the sulphates, carbonates, and phosphates of the alkaline earths 

 are insoluble, it was impossible to modify the precipitating power of 

 the soluble salts of the alkaline earths by the addition of the alkali- 

 sulphates, carbonates, and phosphates, but the effect of adding the 

 alkali salt with monovalent an-ions was studied. 



As shown on p. 288, certain salts may help in or may interfere with 

 the precipitation of egg-white by other salts of the alkalies. Thus NaCl, 

 NaN0 3 , NaB augment, while Nal, NaCNS dimmish precipitation. 

 On the assumption that the kat-ions favour precipitation while an-ions 

 do the opposite, it was further pointed out by Pauli, for the salts of 

 alkalies that Li>Na>K>NH 4 >Mg, and that the an-ions came in this 

 order : CNS > I > Br > N0 3 > Cl > C 2 H 3 2 . 



The alkaline earths differ from the alkalies, because in them the 

 precipitating power of any kat-ion is increased by the an-ions in this 

 order: C 2 H 3 2 >Cl>N0 3 >Br>I>CNS; in other words, the order 

 which holds good for the alkalies becomes reversed for the alkaline 

 earths, and this is attributed to the fact that the originally neutral 

 reaction of the solutions of the alkaline earths are rendered acid by 

 the albumin, which is quite analogous to the above-mentioned observa- 

 tion of Whitney and Ober, who worked with arsenic trisulphide. 

 Whitney and Ober's articles have escaped apparently Pauli. 



That, however, the albumin is not the only factor in altering the 

 neutral reaction of the salts of the alkaline earths into an acid one is 

 shown by the fact that the alkaline reaction of a radium carbonate 

 solution may become neutral and even acid towards phenol-phthalein by 

 the simple addition of neutral calcium chloride (Pauli). As sodium 

 carbonate and sodium phosphate are always present in egg-white, one 

 might expect the reaction of the albumins to be strongly alkaline, 

 owing to the hydrolytic dissociation of the alkali salt into, for example, 

 NaOH + H 2 C0 3 , of which the former, by electrolytic dissociation, gives 

 rise to the strongly alkaline OH'-ion. The action of egg-white being 

 neutral towards phenol phthalein, it follows that the OH radicals must 

 somehow be satisfied by the albumin. On adding a salt of an alkaline 

 earth to an albumin solution, Pauli believes the OH radicals, previously 

 held by the albumin, to now attach themselves to the earthy kat-ions, 

 Ca(OH) 2 , Ba(OH) 2 , Sr(OH 2 ), and thereby to relatively increase the 

 number of the acid H-ions, and so to produce the acid reaction. 



