Specification of Dugald Campbell : treating sewage, &c.

  • Campbell, Dugald.
Date:
1872
Catalogue details

Licence: Public Domain Mark

Credit: Specification of Dugald Campbell : treating sewage, &c. Source: Wellcome Collection.

    5/10 (page 3)
    Campbell's Improved Frocess for Treating Sewage, 8fc. performed, to be particularly described and ascertained in and by the following statement:— Hitherto acid solutions of the natural phosphates of alumina or of the natural phosphates containing either phosphate of iron or phosphate 5 of lime, or mixtures of the same, or of the natural phosphates containing mixtures of phosphates of alumina and phosphate of iron, or of the natural phosphates, containing mixtures of phosphate of lime or of phosphate of iron or of phosphate of lime, either with or without the addition of lime or of chalk, have been proposed to he employed in the 10 treatment of sewage so as to obtain a precipitate of the same, which precipitate is to he employed as a manure, hut in most cases of such treatment the result has been the production of a precipitate containing more or less of phosphate of alumina or of phosphate of iron, these phosphates of alumina or of iron being great or little in the precipitate, 15 according to the natural phosphate used in preparing the acid phosphate so employed in such treatment of the sewage, containing little or much of the oxides of alumina or of iron. Now experience has shewn that either of these precipitated phosphates, namely, the phosphate of alumina or the phosphate of iron, although valuable to some extent 20 for agricultural purposes, are very inferior in this respect to precipitated phosphate of lime, the phosphate of alumina and phosphate of iron being both not easily decomposible by plants, owing no doubt to the bases of these phosphates, namely, alumina or oxide of iron forming practically little or no part of the food of plants. 25 Now my Invention consists in applying for the purpose of obtaining a precipitate from sewage as free - or as nearly free as it is possible from either the phosphate of alumina or the phosphate of iron, artificial or manufactured phosphates of lime which are of themselves practically free from alumina or oxide of iron instead of applying solutions of 30 these natural phosphates, to which I have herein-before referred, as and to obtain a precipitate to he employed as a manure, and I treat the said artificial phosphates of lime in the following manner:—I act upon the said artificial or manufactured phosphates of lime with some mineral acid so as to render the phosphate of lime soluble, and in preference 35 to others by either sulphuric or hydrochloric acid as being more economical than most other such acids, and I apply the compound so obtained, or a solution of the same, adding before or after, but pre¬ ferably after, either a milk or cream of lime, or preferably when it is