A series of chemical problems with key for use in colleges and schools / by T.E. Thorpe. Rev. and enl. by W. Tate ; with a preface by H.E. Roscoe.

Thomas Edward Thorpe

Date:: 1891

Credit: A series of chemical problems with key for use in colleges and schools / by T.E. Thorpe. Rev. and enl. by W. Tate ; with a preface by H.E. Roscoe. Source: Wellcome Collection.

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$3-^ Then DEDUCTION OF 70'0I 56 1-2514 29-99 16 I -8744 The ratio between 1-2514 ; 1-8744 :: i : 1-5 The sim]5lest ratio, in whole numbers, is therefore 2 : 3. I Icncc the formula of the body is Fe2f^.r FORMUL/E OF MINERAI.S. There exist many groups of minerals of which the in- dividual members are composed of ecpial numbers of atoms similarly combined, and which possess the same or nearly the same crystalline form ; such groups arc termed isomor|)hous groups, and the minerals forming each group are said to l)c isomorphous with each other. Isomorphous minerals may i-cpiacc each other without affecting the exterior form of the mineral partially re- placed. As the percentage amount of the elements in such minerals is different in each case, mixed minerals do not admit of being directly represented by a simple formula derived as above fi'orn the percentage composition. It is the practice to icprcscnt minerals of this type by a general formula obtained by considering the particular iso- morphous substance ])rcsent in greatest quantity as the typical substance and reducing the quantities of the re- placing bodies to ec[uivalent quantities of the typical bod_\-, when the formula may be at once obtained by the ordin- ary means. When possible, mineral analyses arc ordinarily rci)ortcd as jiercentages of oxides, and in the calculation these oxides are consiilered as the isomor])hous components to be reduced to terms of that present in greatest amount. As an example we may consider the case of ankcrite : an analysis of which by Schrdttcr yielded the following results :$