580 Analysis of Books, $c. 



rine to a low temperature, was considered as the gas itself reduced into 

 that form. Davy first corrected the error, and showed it to be a hydrate, 

 the pure gas not being condensible even at a temperature of 40 Fahren- 

 heit. Mr. Faraday had taken advantage of the cold season to procure 

 crystals of this hydrate, and was proceeding in its analysis, when Sir H. 

 Davy suggested to him the expediency of observing what would happen 

 if it were heated in a close vessel ; but this suggestion was made after Mr. 

 Faraday had obtained results which must have led him to the experiments, 

 had he never communicated with SirH. Davy. On exposing the hydrate, 

 in a tube hermetically sealed, to a temperature of 100, the substance 

 fused, the tube became filled with a bright yellow atmosphere, and on 

 examination was found to contain two fluid substances : the one, about 

 three-fourths of the whole, was of a faint yellow colour, having very much 

 the appearance of water; the remaining fourth, was a heavy bright 

 yellow fluid lying at the bottom of the former, without any apparent 

 tendency to mix with it. By operating on the hydrate in a bent tube 

 hermetically sealed, Mr. F. found it easy, after decomposing it by a heat 

 of 100, to distil the yellow fluid to one end of the tube, and thus to sepa- 

 rate it from the remaining portion. If the tube was now cut in the 

 middle, the parts flew asunder, as if with an explosion, the whole of the 

 yellow portion disappeared, and there was a powerful atmosphere of 

 chlorine produced; the pale portion, on the contrary, remained, and, 

 when examined, proved to be a weak solution of chlorine in water, with 

 a little muriatic acid, probably from the impurity of the hydrate used. 

 When that end of the tube, in which the yellow fluid lay, was broken under 

 ajar of water, there was an immediate production of chlorine gas. Mr. 

 Faraday soon perceived that the chlorine had been entirely separated from 

 the water by the heat, and condensed into a dry fluid by its own abun- 

 dant vapour. He subsequently confirmed these views by condensing chlo- 

 rine in a long tube by mechanical pressure.' 



To Mr. Faraday's paper, Sir H. Davy thought proper to add a 

 ' note on the condensation of muriatic gas into the liquid form ;' 

 and on the 17th of April, he communicated to the Royal Society a 

 paper * On the application of Liquids, formed by the condensation 

 of Gases, as Mechanical Agents;' which contains the results of several 

 experiments made, with the assistance of Mr. Faraday, on the differ- 

 ences between the increase of elastic force in gases under high and 

 low pressures. 



In the latter part of 1823, the government requested the advice 

 of the President and Council of the Royal Society, as to the best 

 mode of manufacturing copper sheets, or of preserving them, while 

 in use as the sheathing of ships, against the corrosive effects of oxi- 

 dation. Sir H. Davy charged himself with this inquiry, and com- 

 municated the results in three memoirs, read in January and June, 

 1824, and in June, 1S25. In these papers he comes to the con- 

 clusion, that as copper is but weakly positive in the electro-chemical 

 scale, and can only act upon sea-water when in a positive state, 

 that by rendering it slightly negative, the corroding action of 

 sea-water upon it is prevented ; he proposed therefore to render 

 the copper electro-positive by means of the contact of an easily 

 oxidable metal. Having communicated his views to his Majesty's 

 government, an order was made for trying the plan of protection he 



