t40 PHILOSOPHICAL TRANSACTIONS. [ANNO 1797. 



Having found that nitre would dissolve gold, I tried whether it would produce 

 any effect on platina. It has been formerly observed that the grains of platina, in 

 the impure state in which it is originally found, might, by being long heated in a 

 crucible with nitre, be reduced to powder. Lewis, from his own experiments and 

 those of Margraaf, thought that the iron only which is contained in the grains of 

 platina was corroded by the nitre. But by heating nitre with some thin pieces of 

 pure platina in a cup of the same metal, I found that the platina was easily dis- 

 solved, the cup being much corroded, and the thin pieces entirely destroyed. By 

 dissolving the saline matter in water, the greater part of the platina was precipitated 

 in the form of a brown powder. This powder, which was entirely soluble in ma- 

 rine acid, consisted of the calx of platina, combined with a portion of alkali, 

 which could not be separated by being boiled in water. The platina which was 

 retained by the alkaline solution communicated to it a brown-yellow colour. By 

 adding an acid to it a precipitate was formed, which consisted of the calx of pla- 

 tina, of alkali, and of the acid which was employed. 



Silver, I found to be a little corroded by nitre. But as its action on *hat metal 

 was very inconsiderable, it did not appear to be deserving of a more particular 

 examination. 



XII. Experiments to determine the Force of Fired Gunpowder. By Benjamin 

 Count of Rumford, F. R. S., M. R. I. A. p. 222. 



Several eminent philosophers and mathematicians have, from time to time, em- 

 ployed their attention on this curious subject ; and the modern improvements in 

 chemistry have given us a considerable insight into the cause, and the nature of the 

 explosion which takes place in the inflammation of gunpowder; and the nature and 

 properties of the elastic fluids generated in its combustion. But the great deside- 

 ratum, the real measure of the initial expansive force of inflamed gunpowder, so 

 far from being known, has hitherto been rather guessed at than determined; and no 

 argument can be more convincing to show our total ignorance on that subject, than 

 the difference in the opinions of the greatest mathematicians of the age, who have 

 undertaken its investigation. The ingenious Mr. Robins, who made a great num- 

 ber of very curious experiments on gunpowder, and who I believe has done more 

 towards perfecting the art of gunnery than any other individual, concluded, as the 

 result of all his inquiries and computations, that the force of the elastic fluid gene- 

 rated in the combustion of gunpowder is lOOO times greater than the mean pressure 

 of the atmosphere.* But the celebrated mathematician Daniel Bernouilli deter- 

 mines its force to be not less than 10,000 times that pressure, or 10 times greater 

 than Mr Robins made it. 



more strongly to the imperfect nitrous acid, in consequence of their attraction for water when they are 

 united. — Orig. 



* Mr. Robins' s experiments in proof of this, in his New Principles of Gunnery, are very simple ; 

 and sufficiently convincing to show that his number, 1000, is not very greatly wide of the truth in the 

 small quantities he used. In fact it is gradually increased a little more, as the quantity of powder fixed 

 is greater, tiH the number increase to near 2000 times the pressure of the atmosphere. 



