IV.c. ON SOLUBILITY. 811 
nitrates, &c., of these metals. In the main their results were difficult 
to interpret, owing to many of the salts forming various hydrates, but 
in the series—lithium chlorate, bromate, and iodate—the molecular 
solubility was found to decrease in the order given. 
An interesting parallelism in the properties of analogous salts was 
1900 disclosed by the research of Funk.*® This author compared the 
solubility of the hydrates of the selenates, molybdates, and 
tungstates of sodium with the sulphates, and found that all four deca- 
hydrates have parallel solubility graphs. The graph for the solubility 
of the anhydrous selenate is parallel with that of the sulphate; the 
graphs of the dihydrates of the molybdate and tungstate are also parallel. 
Cavalier and Prost ** compared the behaviour of the trialkyl phos- 
phates, and their results showed that the solubility of these compounds 
decreases with increasing molecular weight of the alkyl group: whilst 
the methylic and ethylic esters are miscible with water in all proportions, 
the butylic ester is very sparingly soluble. 
1901 Meusser ** found that the solubility graphs for corresponding 
’ hydrates of cobalt and nickel iodates are closely parallel. A 
study of the solubility of the alums (sixteen in number) enabled 
Locke '!? to deduce an equation expressing their solubility: an equation 
said to be of general application and to depend upon the atomic weight 
of the tervalent element and upon that of the univalent metal in the 
compound. In opposition to these views, mention must be made of the 
results obtained by Yarugi and Checchi.'°? ‘These authors measured 
the solubility of succinates, cinnamates, benzoates, and salicylates of 
magnesium, calcium, strontium, and barium, and expressed themselves 
as unable to deduce any simple relationship between solubility and 
atomic weight of the metals. Almost at the same time Rossi °° pro- 
fessed to have discovered the existence of a relationship between the 
solubility of salts of the same series and their molecular weights. 
1902 After carefully studying the solubility of a large number of 
* double sulphates of the type M’, M” (SO,),6H,O, Locke 14° 
came to the conclusion that the order of solubility is not the order of 
atomic weight, but that the influence of each metal on the solubility of a 
salt is specific and manifest in all its compounds. 
Rossi had stated that when two salts of the same acid, containmg 
similar metals, are compared, the ratio of their molecular weights is a 
multiple of the ratio of their solubilities. Rabe '*”7 sought evidence of 
some such regularity among the salts of thallium but without success : 
he did, however, observe a simple relationship between the molecular 
solubility of thallous and potassium salts. 
1903 According to Groschuff }°? the reverse of the usual order of 
* the alkali metals is obtained when their anhydrous formates are 
tabulated in the order of increasing solubility, the order then being 
Li. Na. K. 
Tutton '®° found the solubility of ammonium sulphate to be very 
close to that of rubidium sulphate. 
Stanley 1** compared the solubility of the formates of the 
1904. stkaline-earth metals and found that the graphs for anhydrous 
barium formate and for the dihydrate of strontium formate both have 
