quantity of very pure ammoniacal gas*: a great expansion of the aëriform matter took place, and a white substance formed, which collected on the sides of the glass tube employed in the process; and this matter, exposed to the action of diluted muriatic acid, effervesced, so that it was probably carbonate of ammonia. A process of another kind offered still more decisive results. In this the two mercurial gazometers of the invention of Mr. Pepys, described in No. XIV. of the Phil. Trans. for 1807, were used with the same apparatus as that employed by Messrs. Allen and Pepys for the combustion of the diamond, and these gentlemen kindly as sisted in the experiment. Very pure ammoniacal gas was passed over iron wire ignited in a platina tube, and two curved glass tubes were so arranged as to be inserted into a freezing mixture; and through one of these tubes the gas entered into the platina tube, and through the other it passed from the platina tube into the air-holder arranged for its reception. The temperature of the atmosphere was 55°; but it was observed that no sensible quantity of water was deposited in the cooled glass tube transmitting the unal * The apparatus in which this experiment was made is described. in page 214, Journal of the Royal Institution. The gas was confined by mercury which had been previously boiled to expel any moisture that might adhere to it. The ammonia had been exposed to the ac tion of dry pure potash, and a portion of it equal in volume to 10980 grains of mercury, when acted on by distilled water, left a residuum equal to nine grains of mercury only. So that the gas, there is every reason to believe, contained no foreigu aëriform mat. ter; for even the minute residuum may be accounted for, by suppasing it derived from air dissolved in the water. tered tered ammonia, but in that receiving it after its ex posure to heat moisture was very distinct, and the gas appeared in the air-holder densely clouded. This circumstance seems distinctly to prove the formation of water in this operation for the decomposition of ammonia; unless indeed it be asserted that the hydrogen and nitrogen gasses evolved hold less water in solution or suspension than the ammonia decomposed; an idea strongly opposed by the conclusions of Mr. Dalton * and the experiments of Messrs. Desormes and Clement t. After the gas had been passed several times through the ignited tube from one gazometer to the other, the results were examined. The iron-wire became converted superficially into, oxyd, and had gained in weight ros parts of a grain; about four-tenths of a grain of water were collected from the cooled glass tubes by means of filtrating paper, and 33.8 cubic inches of gas were expanded into 55.3 cubic inches, and by denonation with oxygen it was found that the hydrogen gas in these was to the nitrogen as 3.2. to one volume. It will be useless to enter into the more minute details of this experiment, as no perfectly accurate data for proportions can be gained from them; for the whole of the ammonia was not decomposed, and as the gas had been prepared by being sent from a heated mixture of sal ammoniac and quick-lime into the air-holder, it was possible that some solution of ammonia might have been deposited, which, by giving out new gas during the operation, would increase the absolute quantity of the material acted upon. * Manchester Memoirs, vol. V. Part II. p. 535, 1785. + Annales de Chemie, vol. XLII. p. 125. In examining the results of M. Berthollet's, elaborate experiments on the decomposition of ammonia by electricity, I was surprised to find that the weight of the hydrogen and nitrogen produced rather exceeded than fell short of that of the ammonia considered as decomposed, which was evidently contradictory to the idea of its containing oxygen. This circumstance, as well as the want of coincidence between the results and those of Priestley and Van Marum on the same subject, induced me to repeat the process of the electrization of ammonia; and I soon found that the quantities of the products in their relations to the apparent quantity of gas destroyed were influenced by many different causes. Ammonia procured over dry mercury from a mixture of dry lime and muriate of ammonia, I found deposited moisture upon the sides of the vessel in which it was collected, and in passing the gas into the tube for electrization, it was not easy to avoid introducing some of this moisture, which must have been a saturated solution of ammonia, at the same time. In my first trials made upon gas, passed immediately from the vessel in which it had been collected into the apparatus, I found the expansion of one of ammonia vary in different instances from 2.8 to 2.2 measures, but the proportions of the nitrogen and hydrogen appeared uniform, as determined by detonation of the mixed gas with oxygen, and nearly as one to three in volume. To exclude free moisture entirely, I carefully prepared ammonia in a mercurial air-holder, and after it had been some hours at rest, passed a quantity of it into the tube for decomposition, which had been filled with * Mémoires de l'Academie, 1785, p. 324. VOL. XIII.-SECOND SERIES. C c dry dry mercury. In this case 50 parts became 103 parts by electrization, and there was still reason to suspect sources of error. I had used iron wires not perfectly free from rust for taking the spark, and a black film from the mercury appeared on the sides of the tube. It was probable that some ammonia had been absorbed by the metallic oxyds both upon the iron and the mercury, which might again have been given out in the progress of the operation. I now used recently distilled mercury, which did not leave the slightest film on the glass tube, and wires of platina. The ammonia had been exposed to dry caustic potash, and proved to be equally pure with that mentioned in page 191; 60 measures of it, each equal to a grain of water, were electrized till no farther expansion could be produced; the gas filled a space equal to that occupied by 108 grains of water. The thermometer in this experiment was at 56o, and the barometer at 30.1 inches. The wire of platina transmitting the spark was slightly tarnished *. The 108 measures of gas, carefully analyzed, were found to consist of 80 measures in volume of hydrogen, and 28 measures of nitrogen. The results of an experiment that I made in 1799 + give the weight of 100 cubic inches of ammonia, as 18.18 grains at the mean temperature and pressure. I had reasons, however, for suspecting that this estimation might be somewhat too low; and on mentioning the circumstance to Messrs. Allen and Pepys, they kindly undertook the examination of the subject, and Mr. This most probably was owing to oxydation. When platina is made positive in the Voltaic circuit in contact with solution of ammonia it is rapidly corroded. This is an analogous instance. + Researches Chem. and Phil. p. 62. Allen Allen soon furnished me with the following data. "In the first experiment 21 cubic inches of ammonia weighed 4.05 grains; in a second experiment the same quantity weighed 4.06 grains, barometer 30.65, thermometer 540 Fahrenheit." Now if the corrections for temperature and pressure be made for these estimations, and a mean taken, 100 cubic inches of ammonia will weigh 18.67 grains, barometer being at 30, and thermometer at 60° Fahrenheit; and if the quantity used in the experiment of decomposition be calculated upon as cubic inches, 60 will weigh 11.2 grains. But the hydrogen gas evolved equal to 80 will weigh 1.93 grains, and the nitrogen equal to 28 †, 8.3. And 11.2, grains 1.98.3 10.2 and 11.2 10.2.1, all the estimations being, made according to the standard temperature and pressure. - So that in this experiment on the decomposition of ammonia the weight of the gases evolved is less by nearly one-eleventh than that of the ammonia employed; and this loss can only be ascribed to the existence of oxygen in the alkali; part of which probably combined with the platina wires employed for electrization, and part with hydrogen. After these ideas the oxygen in ammonia cannot well be estimated at less than seven to eight parts in the hundred; and it possibly exists in a larger proportion as the gases evolved may contain more water than the gas de *Lavoisier's Elements, p. 569. A cubical inch of hydrogen is considered as weighing .0239. + Researches Chem. and Phil. p. 9. From my experiments 100 cubical inches of nitrogen weigh at the standard temperature and pressure 29.6 grains. |