from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Containing three replaceable hydrogen atoms per molecule. Used of an acid.
- adj. Containing three univalent basic atoms or radicals per molecule. Used of a base or salt.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. containing three replaceable hydrogen atoms
- adj. having three atoms of a univalent metal
from the GNU version of the Collaborative International Dictionary of English
- adj. Capable of neutralizing three molecules of a monacid base, or their equivalent; having three hydrogen atoms capable of replacement by basic elements on radicals; -- said of certain acids; thus, citric acid is a tribasic acid.
from The Century Dictionary and Cyclopedia
- In chem., having three hydrogen atoms replaceable by equivalents of a base: noting some acids.
Sorry, no etymologies found.
Similarly, we may have tribasic and tetrabasic acids.
Being a tribasic acid, it forms acid as well as normal salts.
In the commonest form, popularly called bone-phosphate, which is the form in which lime and phosphoric acid are combined in bones, guano, and the ordinary mineral phosphates, the lime and phosphoric acid are combined in the form of what is known as tribasic phosphate of lime, or tricalcic phosphate -- that is to say, for every equivalent of phosphoric acid there are three equivalents of lime.
The ordinary or medium class contains from 25 to 27 per cent of soluble phosphate; and here it may be pointed out that by soluble phosphate is meant the percentage of tribasic phosphate which has been dissolved -- not, as might at first sight be supposed, the percentage of monocalcic phosphate.
Now it was naturally concluded at first that the tribasic phosphate was the form in which these two substances existed in the slag.
Contrary to what we might expect, this phosphate is less insoluble than the ordinary tribasic or bone phosphate.
According to Rose, apatite is made up of three molecules of tribasic calcium phosphate (Ca (PO_4) _2), combined with one molecule of calcium fluoride (Ca F_2) or one molecule of calcium chloride (CaCl_2) respectively.
The larger the percentage of tribasic phosphate, the larger the quantity of sulphuric acid required for its decomposition; but sometimes even a poor phosphate consumes a large amount of sulphuric acid.
In the ordinary so-called raw phosphates, such as bone-meal, bone-ash, coprolites, &c., the lime and phosphoric acid are combined in the form of what is known, in chemical phraseology, as _tribasic phosphate of lime_.
 The solubility of tribasic phosphate, of course, is not always equal in different manures.