This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1869 Excerpt: ...2 equivalents, the third 3 equivalents. These are the true phosphoric acids, and it will be seen that they differ in composition. Graham, therefore, designated them by different names, which they have retained, and nobody at the present day thinks of regarding them as isomeric. Their salts are analogous in composition ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1869 Excerpt: ...2 equivalents, the third 3 equivalents. These are the true phosphoric acids, and it will be seen that they differ in composition. Graham, therefore, designated them by different names, which they have retained, and nobody at the present day thinks of regarding them as isomeric. Their salts are analogous in composition to the acids themselves. The monohydrated acid takes up 1 equivalent of oxide, the trihydrated acid takes up 3 equivalents. The former gives with nitrate of silver a white, the latter a yellow precipitate. These differences, which had struck the first observers, exhibit nothing abnormal, for they are due to differences of composition. The white precipitate, or Note 16, p. 206. metaphosphate of silver, contains 1 atom of silver; the yellow precipitate, or ordinary phosphate of silver, contains 3 atoms. This is expressed by saying that metaphosphoric acid is monobasic; ordinary phosphoric acid, tribasic. We have thus arrived at the point which we wish to bring to light. There are some acids whose molecule is so constituted as to require for saturation only one ' equivalent' of a certain base, whereas other acids take up two equivalents, and others again require three. Have, then, the molecules of these acids the same value? and are they equivalent among themselves? By no means, since their capacity of combination, expressed by the proportions of base which they saturate, varies as the numbers 1, 2, and 3. Let us compare together nitric, sulphuric, and phosphoric acids. To form a perfectly saturated salt the first combines with one molecule of potash, the second with two, the third with three molecules; and if we regard as equivalent the molecules of acids which saturate the same quantity of base, we shall be obliged to admit that 1 molecule of s...
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