though non-flaming chip of wood, which immediately bursts into flame. Oxygen gas is essentially the supporter of animal life, yet no animal can live for a protracted time in undiluted oxygen. Assuming water to be the protoxide of hydrogen, then it follows that the atomic or combining volume of oxygen gas is only half that of hydrogen. One hundred cubic inches of oxygen gas under a barometric pressure of 30 inches, and at a temperature of 60° F., weigh 34.6 grains; 100 cubic inches of air, under similar conditions, weighing 31.0117 grains. Hence, the specific gravity of oxygen, air being unity, will be equal to 1-111. It is 16 times heavier than hydrogen gas, but its combining volume being only half the combining volume of hydrogen, it follows that, considering hydrogen to be the unity of atomic comparison, the atomic or equivalent weight of oxygen will be 8; and here it may be remarked that a consideration of the combining volume of gases, and of their combining weights, furnish the data, when taken in connection with the specific gravity of hydrogen, for indicating the specific gravity of any particular gas. If the atomic or combining volumes of all gases were equal, then the numeral ratio of their atomic weights would be also the ratio of their specific gravities; but as the combining volumes of gases are unequal-are, viz., oxygen possessing a combining volume half that of hydrogen, and several others double that of hydrogen-this circumstance must be made an element in the calculation. = Applying the rule to determine the specific gravity oxygen, the operation is as follows :— of * Possibly, according to modern researches, 0·693. Mixture of chlorate of potash with oxide of manganese, glass retort, spirit-lamp, ring-stand, pneumatic trough, and glass jars. Bottles and jars of oxygen. Table of the weight of oxygen. Binoxide of nitrogen in jar over a pneumatic trough. Prove that it is a test for oxygen; then prove the existence of oxygen in the atmospheric air. Phosphorus (clean) in a funnel; phosphorus (clean) in a bottle; with a little water for the production of ozone. Phosphorus, and a little disc of chalk on which the phosphorus may be lighted. A jar of oxygen for displaying the combustion of phosphorus. A jar of oxygen for displaying the combustion of charcoal. Bottles of ozonized air, and mode of its preparation. Paper imbued with iodide of potassium and starch. Silver leaf in bottle. Ether-jar and hot glass rod. The ozonometer of Schönbein described. Specimens of rock crystal. Flint sand. Tables of their composition. Specimens of granite, clay, slate. Silicified wood. Phosphorus thrown into water. Potassium thrown into water. Specimens of nitre and of chlorate of potash. Tables of their composition. Chlorate of potash and sulphuret of antimony or sugar. ALTHOUGH in these lectures it has never been professed by the directors of the Royal Institution to present a F strictly systematic course of instruction, yet it has been always considered an object to avoid adopting the opposite course. It has been thought desirable also to avoid desultory teaching, and to so arrange the various discourses that, although delivered by various persons, and on various subjects, they may yet form an alliance with each other, and present a tolerably connected scheme in the end. Influenced by this consideration, I have been induced to select the non-metallic elements, or the zootic elements, as a modern writer has termed them, as the subject of the present lectures, because the metallic elements have been recently discussed in the other theatre by Mr. Mansfield, and chemistry, as applied to the industrial arts, by my colleague, Mr. Brande. I do not propose to treat the subject in a purely chemical sense; to discuss the non-metallic elements in the order of their discovery; to pass under notice the various theories of which these elements have been the subjects, or even to make known all their minuter characteristics. My object is rather to treat of them broadly; to point out their more striking features; to consider them not only as chemical agents, but as fulfilling each its appointed function in the material universe. First, then, what do we mean by the term element? By it chemists understand, not a body incapable of subdivision into constituents, for this assumption would imply a belief that the decomposing agencies of chemistry had already attained their finality, -that we had reached the limits of decomposition,that further progress in this direction would be impossible;-by the term element chemists understand any kind of matter which, up to the present time, has never been decomposed into constituents: hence such matter is considered to be an element provisionally, and subject to future modification. Of these elements we are at this time acquainted with sixtytwo or sixty-three, of which the names are given in a diagram: |