258 Mr. M 'Mullen on the Existence of Chlorine 



Ramsden. Their power can be varied. Each instrument 

 carries six, five of which can be attached at pleasure either to 

 the catadioptric or the achromatic. The deepest belonging to 

 the reflector is a single lens of half a French line focus, and the 

 most powerful of the achromatic is a line and a half. 



" Such, we think, are the details which you required : we 

 wish that they may prove agreeable to you, 



"We beg you to accept the assurance of the high considera- 

 tion with which we are, Sir, 



♦' Your very devoted Servants, 



*' Vincent Chevalier, aine et fils," 



**69, Quai de THorloge:" 



On the Existence of Chlorine in the Native Black Oxide of 

 Manganese. By John M'Mullen, Esq. 



In the paper relating to this subject, which the editors of the 

 Quarterly Journal of Science obligingly inserted in the forty- 

 fourth number of that work, I described some experiments 

 which I had made, to show that chlorine is uniformly evolved 

 from the Native Black Oxide of Manganese by the action of sul- 

 phuric acid, under certain circumstances, which I endeavoured 

 to detail with strict accuracy, so as to prevent any mistake or 

 failure in the event of the experiment being repeated. 



Upon this paper Mr. Richard Phillips has made some obser- 

 vations in the Philosophical Magazine and Annals of Philoso- 

 phy for April last, to which I am desirous of briefly adverting. 

 He says, " Mr. M'MuUen having observed, when sulphuric 

 acid is added to peroxide of manganese, that chlorine is evolved, 

 he conceived it might be derived from an admixture of muriate 

 of manganese, iron, or copper ; but having washed some of the 

 peroxide of manganese with water, he did not find that any 

 chloride of silver was precipitable from it ; he, therefore, con- 

 cluded that the peroxide in question contained no muriatic 

 salt." If Mr. Phillips will take the trouble to refer to my 

 paper, he will find that this is by no means the statement which 

 it contains. I obser\ ed that, in order to separate any soluble 



