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1818.] I have not examined the action of ammonia upon the other chlorides; with some of them it would probably form neutral compounds, with other combinations similar to those described. Nearly all those mentioned are formed by the exertion of an affinity so weak that it is overcome by the attraction of water for the ammonia, and yet in one instance it is capable of giving a definite crystalline form.

The facility with which many of them afford dry ammoniacal gas at low temperatures in considerable quantities, may perhaps in some cases make them convenient sources of that substance ; 19 grains of the compound with chloride of lime which had been made many days, gave l9.4 cubical inches of gas. They also offer a convenient means of ascertaining the specific gravity of ammonia, by the quantity of gas given off, and the loss of weight in the substance.

is an experiment usually made in illustration of the properties of hydrogen gas, which was first described by Dr. Higgins in the year 1777, and in which tones are produced by burning a jet of hydrogen within a glass jar or tube. These tones vary with the diameter, the thickness, the length, and the substance of the tube or jar; and also with changes in the jet. They have frequently attracted attention, and some attempts to explain their origin have been made.

After Dr. Higgins, Brugnatelli in Italy, and M. Pictet at Geneva, described the experiment, and the effects produced by varying the position and other circumstances of the jet and tube; and M. De la Rive read a paper at Geneva (published in the 'Journal de Physique,' lv. 165), in which he accounted for the phenomenon by the alternate expansion and contraction of aqueous vapour. That they are not owing to aqueous vapour, will be evident from some experiments to be described. I have no doubt they are caused by vibrations, similar to those described by M. De la Rive; but the vibrations are produced