On mingling a large quantity of caustic solution of ammoniac with ¼ of its weight of water, of exactly the same temperature, no alteration of it was perceptible by a sensible thermometer.—Hence the two experiments[69] being assumed as data, the intermediate estimations in the following table, were found by calculation. [69] Previous to those experiments, I had made a number of others on the combination of ammoniac with water.—My design was, to ascertain the diminution of specific gravity for every three grains of ammoniac absorbed; but this I found impossible. The capillary tube, when taken out of the phial, always carried with it a minute portion of the solution, which partially evaporated before it could be again introduced; and thus the sources of error increased in proportion to the number of examinations. TABLE IV. _Of approximations to the quantities of AMMONIAC, such as exists in the aëriform state, saturated with water at 52°, in AQUEOUS AMMONIACAL SOLUTIONS of different specific gravities._ +----------+-----+----------+--------+ | 100 | | Ammoniac.| Water. | | Specific | | | | | Gravity. | | | | +----------+ +----------+--------+ | 9054 | | 25,37 | 74,63 | | 9166 | | 22,07 | 77,93 | | 9255 | | 19,54 | 80,46 | | 9326 | c | 17,52 | 82,48 | | 9385 | o | 15,88 | 84,12 | | 9435 | n | 14,53 | 85,47 | | 9476 | t | 13,46 | 86,54 | | 9513 | a | 12,40 | 87,60 | | 9545 | i | 11,56 | 88,44 | | 9573 | n | 10,82 | 89,18 | | 9597 | | 10,17 | 89,83 | | 9619 | | 9,60 | 90,40 | | 9684 | | 9,50 | 90,50 | | 9639 | | 9,09 | 90,91 | | 9713 | | 7,17 | 92,83 | +----------+-----+----------+--------+ As yet no mode has been discovered for obtaining gases in a state of absolute dryness; consequently we are ignorant of the different quantities of water they hold in solution at different temperatures. As far as we are acquainted with the combinations of ammoniac, there is no state in which it exists so free from moisture, as when aëriform, at low temperatures. That no considerable source of error existed in the two experiments, is evident from the trifling difference between the estimations of the quantities of real ammoniac, in the solution of,9684, as found in the first experiment, and as given by calculation from the last. The quantity of ammoniac in a solution of specific gravity not in the table, may be thus determined—find the difference between the two specific gravities nearest to it in the table; _d_, and the difference between their quantities of alkali, _b_; likewise the difference between the given specific gravity and that nearest to it, _c_. then _d_ : _b_ :: _c_ : _x_