524 MM. Svanberg and Struve on the Atomic Weight 



This, and other suggested corrections were, however, never 

 made in any subsequent edition of Simson's Data. There 

 are, in fact, other errata and corrigenda mentioned in these 

 letters which were not corrected in the subsequent editions; 

 and Simson complains in strong language of the "stupid con- 

 duct of John Balfour" in getting the second 8vo edition printed 

 in Edinburgh ; and says that some of it is "so spoiled" as to 

 be unintelligible. I have had no opportunity of collating the 

 earlier editions since these letters were placed in my hands, 

 and can hence offer no distinct opinion as to the corrections 

 of the errors thus introduced. I have done, however, the next 

 best thing, — communicated the errata noticed in these letters 

 to the editor of the best edition of Euclid we possess, Mr. Potts 

 of Cambridge; although from the evident care which that 

 gentleman has bestown upon his work, I think it likely that 

 few, if any of them, will have previously escaped his scrutiny. 



I propose in the next sections to give three original letters 

 from John Bernoulli to Cramer. Their length, however, will 

 preclude the possibility of the slightest comment. 



Royal Military Academy, Woolwich, 

 November 8, 1848. 



- =*~ 



LXXVI. On the Atomic Weight of Molybdenum and some of 



its Compounds. By L. Svanberg and H. Struve. 



[Continued from p. 434.] 



Part II. 



Behaviour of Molybdic Acid towards Phosphoric Acid. 



A LTHOUGH the behaviour of molybdic acid towards 

 •t*~ phosphoric acid was not intimately connected with the 

 object of our investigation, yet we were so frequently led to it 

 that we considered it necessary to make some experiments 

 upon the subject. This behaviour is so peculiar and so com- 

 plicated that it requires a far more minute examination than 

 we were able to devote to it, but since we have noticed some 

 phenomena which have not hitherto been described, we con- 

 sider it important to communicate in this place all that we 

 have observed. The curious behaviour of molybdic acid to- 

 wards phosphoric acid has been briefly noticed by some che- 

 mists. Berzelius* says, " When moist molybdic acid is mixed 

 with phosphoric acid, it instantly becomes of a lemon colour; 

 heat then dissolves it. The filtered liquid is colourless, and 

 on evaporation leaves a tenacious transparent mass, which 

 exhibits not the least sign of crystallization, and possesses a 

 * Lehrbuch der Chemie, 1845, vol. iii. p. 1044. 



