PHILOSOPHICAL TRANSACTIONS. 
I. The Monoclinic Double Sulphates Containing Ammonium. 
Completion of the Double Sulphate Series. 
By A. E. H. Tutton, D.Sc., M.A., F.R.S., President of the Mineralogical Society. 
Received June 8,—Read June 17, 1915. 
In this communication are described the five remaining double sulphates of the series 
R 2 M(S0 4 ) 2 .6H 2 0, in which R. is ammonium and M is nickel, cobalt, manganese, 
copper, and cadmium. The ammonium salts, in which M is magnesium, zinc, and 
iron, have been described in two previous communications,*! in the latter of which 
(that concerning ammonium ferrous sulphate) a number of general questions 
concerning the whole series were also discussed. The present contribution completes 
the author’s work, commenced in the year 1890, on the double sulphates of this 
important monoclinic series, in all 31 salts, of which the R, bases have been potassium 
rubidium, caesium-, ammonium, and thallium. Excluding thallium—of which only the 
zinc double sulphate has been included, the other double salts containing thallium not 
having yet been obtained in crystals of the perfection necessary for detailed accurate 
work of the character regarded as essential by the author—the four bases, potassium, 
rubidium, caesium, and ammonium should give rise, with the eight several dyad bases 
above enumerated, to 32 double sulphates. All these have been obtained in excellent 
crystals, and fully described, with the two exceptions of potassium manganese and 
potassium cadmium sulphates, which, for some as yet undiscovered reason, are 
incapable of preparation. Yet so thoroughly are the relations between the various 
salts, and the rules governing the replacement of any one alkali base by any other, 
now understood, that it has been found possible to predict the constants of the two 
missing salts. Of the isomorphous double selenates, nine salts (including thallium 
zinc selenate) containing magnesium and zinc as M metals have already been 
described by the author, and it is intended that the remaining double selenates, 
those containing the other dyad metals, shall form the subject of the author’s next 
commun ication. 
* ‘ Journ. Chem. Boc., Trans.,’ 1905, vol. 87, p. 1123. 
t ‘Roy. Soc. Proc.,’ A, 1913, vol. 88, p. 361. 
VOL. CCXVI.-A 538. B [Published October 30, 1915. 
