2/4 Extract from a Memoir 



these numbers is found in a simple ratio with that of the oxygen 

 of the jjliosphoric acid. The simple ratio which they approach 

 the nearest is that of 9 : 10, which will suppose 112--J of oxy- 

 gen in the phosphatic acid. Although the difference between 

 the calculation anil the observation is as much as two centiemes, 

 I tliink it very probal>le, for other reasons about to be explained, 

 that these tuo acids are reallv in this proportion ; and this is 

 what I purpose, besides, to verify directly in another manner. 



It must be observed on this subject, that when, in a series of 

 binary con)pounds formed by the same elements, there are two 

 very much aike, that which is not in a simple relation with the 

 others ought to be considered as a combination of two more 

 simple compounds. It is absolutely indispensable to admit this 

 idea, if we wish to preserve the theory of chemical proportions 

 in all its simplicity: and this is happily what experience con- 

 firms in an evident manner. It is thus, for example, that if we 

 wished to regard the three oxides of iron as primary combina- 

 tions, we must admit at least six molecules of oxygen in the in- 

 ferior oxide, and at least nine in the oxide at the maximum; 

 for the quantities of oxygen contained in these three oxides are 

 as the numbers G, 8, and 9 : but admitting that the intermediary 

 oxide is formed of two molecules of red oxide and one molecule 

 of oxide at the minimum, we are only obliged to suppose that 

 there are two molecules of oxygen in the oxide at the minimum, 

 and three in the oxide at the maximum. This ceases to be a 

 pure supposition when we observe the division into red oxide 

 and protoxide, which the deutoxide of iron presents in almost 

 all experiments *. 



The exact determination of the proportions of the phosphoric 

 acid was indispensable for the analysis of the preceding acids ; 

 and the discordance of the results obtained hitherto by chemists 

 equally expert, imposed upon me the necessity of searching for 

 the causes of error which might exist in the processes resorted 

 to, and to employ others which should be beyond all suspicion. 



I examined in the first place the process of the acidification 

 of phosphorus by the nitric acid, and I saw that it did not merit 



* The second number of the Journal of the Royal Institution of London, 

 which did not appear until after my paper was read,cont:ii[)s an extract from, 

 or rathe;- a severe criticism on, a work written in Swedish by M. Berzelius, 

 in which we find an explanation similar to tliat which I give here. It is a 

 great satisfaction to uie to have coincided with a man of talent so distin- 

 guished. Although I regard this opinion as very probable, I do not pre- 

 tend however that it cannot be combated. But it is not with the ironical, 

 injurious and offensive tme which reigns in the whole of the article just 

 mentioned, that we ought to attack labours the whole object of which is 

 an inquiry after truth. If this kind of criticism is once introduced into 

 the sciences, their progreis will be greatly retarded. 



a)iv 



