66 PATERSOK : EFFLOllEECESCE OF‘ V.I.-E$orescence of Double Ferrous Aluminium Sulphate o n Bricks exposed to Sulphur IIioxide. By DAVID PATEWON. IT is well known that in certain volcanic districts, such as in Sicily, the neighbourhood of Naples, Iceland, Auvergne, and elsewhere, natural alums are found in the shape of white effloresced salts pro- duced by the action of sulphurous rapours on aluminous minerals such as lava or trnchyte. An interesting example of the formation of a similar aluminous salt has been found on the bricks which form the inner v-ail of wool-bleaching chanibers, and which are thus ex- posed to the sulphur dioxide fumes employed i n the bleaching pro- cess. After the bleaching chambers have been in use for a year or so, there appears on various parts of the bricks, wherever there are most bases present, a white flocculent coyeying composed of clusters of glistening crFstalp, often beautifully and regularly crystallised.When such a cluster is broken up, it exhibits a silken or fibrous mass of white crystals resembling Kodule opened, showing crjstalline structure. asbestos in texture. This silken appearanw of these natural efflorescences has supge4ed the Fopular names “ hair salt” and “feather alum.” Their c r j stalline structur2 may be seen from the accomranying drawing tukcn from a specimen. TLcmore perfect of these crystals measured from 9 t o 10 mm. in length. In course of time, the bricks exfoliate ar,d become completely dis- integrated from the formation of crystals within them. When a brick is thus broken down i t is found t o be permeated with sulphur- ous and sulphuric acids, while little tufts of crystals are formed throughout its whole mass.Along with these white carysials, but in very small quantity, is sometimes found a dull, jellowish substance which, on subsequent analysis, was found to contain ferric sulphate. Various specimens of these salts were collected for analysis, and from the results obtained it was found that their composition closely agreed with some of the natural iron alums found in various parts of the world. The following, for instance, is an analysis given many years ago, by Forchhammer, of a natural iron alumiuium sulphizte in Iceland, and, when compared with the analyses of these salts formed on bricks exposed to sulphur dioxide, it will be seen they are very similarly constituted.Iceland Iroia A l ~ m ” (Forchhammer). FeO. Fe,O,. A1,0,. MgO. H2S0,. H,O. Total. 4-57 1.23 11.22 2.19 35-16 45-63 100.00 Samples 1, 2, and 3 were quite white, b u t 4 was OC a dull, yellowish colour owing to the presence of a larger percentage of ferric salt. The results of analysis were as follows :- Sample. Ferrous oxide. ..................... Ferric oxide.. .................... Alumina ......................... Magnesia ........................ Sulphuric acid.. .................. Sulphurous acid .................. Water .......................... Silica! lime, brick> insoluble matter., sulphur ...... i ~ 1. ~~ 5 -53 0 -49 11 *33 1 -06 42 -13 trace 89 *46 - -- I00 .oo 2. --- 5 -38 0 -98 9 -20 0 -65 40 *l4 trace 43 -65 - -- 100 -00 3. -- 5.65 0 -86 11 *45 0 ‘82 41 *09 trace 40 -13 - 4. -- 6-20 2 ‘05 7.96 1 24 39 -50 trace 38.49 4 *56 The above results show that these salts, from their varying com- position, cannot be regarded as definite chemical compounds, as no two analyses agree. If, however, their impurities be not taken into consideration, it will be found they closely resemble, on an average, the formula of a double ferrous aluminium sulphate, AI,(SO,), + FeSO, + 24Aq, as may he seen tlius.63 SCBUKCK AND MXRCHLEWSKI : Fe. Al. Sod. H,O. Irnpui.it,ios. Total. Found.. . . 5.61 5.76 , 4'3*:;7 4 b*:31 1.02 100 07 Theoretical 6-04 5.83 41-46 46.67 - 100.0 The chemical composition of the clay from which these bricks are made is as follows. Si02. A120,. Fe203. CaO. MgO. Alkalis.. H,O. Total. 64.50 14.80 2.05 5-43 6-10 3.FjO 2-65 100.0