218 Intelligence and Miscellaneous Articles. 



laston's, with regard to the sensitive substance guaiacum, which be- 

 comes blue beyond the violet part of the spectrum, and again becomes 

 colourless in the red and yellow rays. 



I have confined myself to the foregoing observations, on the sub- 

 ject of Messrs. Foucault and Fizeau's note, to show that the com- 

 plicated phaenomena produced by the appearance of the Daguerreo- 

 type plates (although very important for the photographic images 

 produced in the camera-obscura, and for the observation of active 

 rays of very little intensity) cannot lead to definite and unvarying 

 results, as regards the nature of the chemical action produced. It is 

 therefore necessary to oj)erate, as has been heretofore done, by means 

 of simple products, with sensitive paper, regard being had to the 

 electrical effect due to the chemical reaction produced under the in- 

 fluence of the solar rays. — Ibid. 



RESEARCHES ON MELLON AND ITS COMPOUNDS. 

 BY MM. AUG. LAURENT AND CH. GERHARDT. 



The authors observe that in their last memoir on this subject they 

 had not repeated the experiments of M. Liebig ; that they had 

 merely modified a part of his theory, the authority of his name ap- 

 pearing to be a sufficient guarantee for the accuracy of his results. 

 According to M. Liebig, this substance is composed of — 



Six atoms of carbon =458"61 39"36 



Eight atoms of azote =708-16 60- 64 



One atom of mellon =1166-77 100-00 



According to him, it is a radicle composed of carbon and azote, 

 capable of uniting with hydrogen, oxygen and metals^jso as to form 

 compounds analogous to those into the composition of which cyano- 

 gen enters. 



The authors state, and they do it with regret, that the reliance 

 which they placed on the results of M. Liebig has totally misled 

 them ; and that it is not a part only of his labours on this subject 

 which is erroneous, but that this is the case with the entire historj"- 

 of mellon, with all its transformations and all its reactions. The 

 authors assert that they are also in a condition to prove that the sup- 

 posed analogy with cyanogen does not exist; for instead of con- 

 sisting only of carbon and azote, mellon contains besides one and a 

 half per cent, of hydrogen. Various processes have been employed 

 for obtaining mellon. That analysed by MM. Laurent and Ger- 

 hardt was obtained very pure by calcining chlorinated cyanamide 

 {cyanamide chloree) as long as hydrochloric acid and hydrochlorate 

 of ammonia were disengaged. 



The following are the results of four experiments performed to 

 ascertain the composition of mellon : — 

 I. II. 



Carbon 36-0 35-8 



Hydrogen 1*7 1-8 



Azote 61-3 62-4 



99-0 1000 1000 10000 



