134 On the Combinations [Feb. 



heterogeneous substances, actually possessed of different specific 

 gravities, according to the old meaning of the term, in their 

 different parts ; because it would be quite contrary to all the 

 calculations of probability, that in so great a number of instances, 

 the accidental errors should all have been exactly of such a 

 nature as to tally precisely with the theory. Nor can I feel any 

 hesitation in absolutely rejecting an idea, which, under other 

 circumstances, would have immediately suggested itself, that 

 the writer, having inadvertently formed an erroneous theory, had 

 endeavoured to prove its truth by a set of fictitious experiments. 

 I am, Gentlemen, your obedient servant, 



Netebold,Jan. 10, 1818. J. L. 



Article XIII. 



Abstract of a Memoir on the Combinations of Phosphorus and 

 Oxygen. By M. Dulong.* 



It is generally supposed that oxygen and phosphorus unite 

 so as to form acids, in two proportions only, and there is still 

 some uncertainty about the proportion of their elements. Lavoi- 

 sier fixed the proportions of phosphoric acid at 100 phosphorus 

 and 154 oxygen; Sir H. Davy coincides with him in these 

 numbers ; but other chemists, as Rose, Berzelius, and Thomson, 

 have obtained different results : Dr. Thomson, from some late 

 experiments, has fixed the proportions at 100 parts of phos- 

 phorus to 123*37 of oxygen. M. Thenard is the only chemist 

 who has made a direct analysis of phosphorous acid ; and he 

 states its components to be 100 parts of phosphorus to 110 of 

 oxygen : M. Gay-Lussac, and Sir H. Davy, on the contrary, 

 suppose it to consist of only 76 parts of oxygen to 100 parts of 

 phosphorus . 



In endeavouring to detect the causes which have led to these 

 various opinions, M. Dulong informs us that he has discovered at 

 least four distinct acids, formed by the union of oxygen and 

 phosphorus. The acid which contains the minimum of oxygen 

 is produced by placing the alkaline phosphurets in contact with 

 water. The phosphurets of strontian and barytes were those 



* Abridged from vol. iii. of the Memoirs of the Society of Arcueil. Tn this 

 abstract will be found the principal facts and opinions which are contained in the 

 elaborate memoir of M. Dulong. It will be perceived that many of his conclusions 

 differ from those of preceding chemists, who have treated upon the same subject, 

 and especially from those of Sir H. Davy. We are informed that this distinguished 

 philosopher has been lately engaged in a series of experiments on phosphorus, the 

 particular object of which is to examine some of the statements which are brought 

 forward by M. Dulong, and which appear to militate against his own. We shall 

 have much satisfaction in taking the earliest opportunity of laying the results 

 before our readers. 



