Although the concentration of SO," would be low relatively to that of SO,H', the SO," seems more Similar reactions could occur with complexes built up likely to be the constituent of the complex ions. with S0,H' ions but would be rather more complicated.

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By HENRY BASSETT and (in part) THOMAS HENRY GOODWIN.The present investigation has followed more or less conventional phase-rule methods so far as the less basic compounds are concerned. The more basic compounds are so insoluble that their study had t o depend much more upon finding satisfactory methods by which they could be prepared. Having found such methods it has been possible to examine their mutual relations and to determine, at least qualitatively, their regions of existence in the phase-rule diagram of the system Al,O,-SO,-H,O.So far as the three-component system is concerned, the stable fields of existence of the more basic compounds are crowded into a very small space in the neighbourhood of the water point. I t is clear that complex ionic, molecular, and micellar equilibria exist involving the numerous basic sulphates. The positions of these equilibria can be altered by change of temperature and are then readjusted only slowly, so that solutions can be obtained which have the same composition but yield different compounds. The system contains a great variety of phases, There are, besides Al,(SO,),, 1 6H,O, a t least eight well-defined crystalline basic sulphates, most of which occur in more than one state of hydration.In addition to these crystalline compounds, there are two quite different sets of two-liquid systems. Both of these form rough ellipses when plotted in an isothermal of the Al,O,-SO,-H,O system. Two-liquid system I is found in a relatively weakly basic region of the three-component system, and the second liquid phase occurs in the form of glassy discs or spheres. Its second liquid phase constitutes the so called hydroxide " precipitates obtained from sulphate solutions with ammonia and the gels thrown down from hydroxide sols with sulphate ions. The recognition of the liquid nature of " hydroxide precipitates" appears to be of some importance. These are (NH,),SO,,[l 1A1,O3,6SO3,xH,O] and 6(NH,),SO,,[llAl,O3,6SO3,xH,O]. The " alunites,"another group of basic double salts, are also important in connection with the system AI,O,-SO,-H,O. These compounds are usually given the formula MI[Al,(OH) a] (SO,),, but such varied types of substitution are possible in the crystal lattice that the composition can differ greatly from that required by the conventional formula. Alunites can exist which contain only Al,?,. SO,, and H,O.The X-ray diagrams of all the compounds obtained during the investigation have been examined, as have those of a number of minerals reputed t o be basic aluminium sulphates. The only basic aluminium sulphate minerals (other than the alunites) which are really welldefined compounds are aluminite '' A1,O,,SO3,9H,O, and a new mineral 2A1,0,,S03,xH,0, which occurs in two different stages of hydration (Bannister and 'Hollingworth, Future, 1948, 162,565).basaluminite ; ! f i e other, with x of the order of 30, has been distinguished by the name These three minerals have perfectly distinct and characteristic X-ray spectra but, for some reason, all our efforts to prepare them synt...

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