TRANSACTIONS Or THE SECTIONS. 85 



On Specimens of Agate and other Natural Colloid /Silica, exhibited hi/ 



G. XJnwin. 



On Dinitrohromlenzene. Bij J. F, "Walker, M.A., F.C.S. 



A series of experiments were made by Dr. Tli. Zincke and myself, to see whether 

 the orthomononitronionobrombenzene (meking-point 125° C.) and the metamono- 

 nitromouobrombenzene (melting-point 30°), when treated with fuming^ nitric 

 acid (spec. grav. I'o) and concentrated snlphuric acid, gave the same modification 

 of dinitromonobrombenzene, and whether one or more modifications were formed 

 by this reaction. 



' We found by treating the orthouitrobrombenzene in this manner, precipitating 

 with water and repeated recrystallization, that only the dinitromonobrombenzene, 

 which melts at 72°, was formed. By treating the metanitrobrombenzene in the 

 same maimer, we only obtained the same modification of dinitrobrombenzene, 

 melting at 72°. 



The melting-point of each crop of crystals was taken. 



The position'of the replaced atoms'^ of hydrogen are not known with certainty, 

 whether they are 1-2 or 1-3 or 1-4. (See Kekuk^ vol. ii. p. 515. )_ 



Both these mouonitrobronizenes are formed by the action of nitric acid on mono- 

 brombenzene. 



If the position of the replaced atom of hydrogen in nionobrombenzene be repre- 

 sented by the letter a, 



the positions of tlie replaced atoms of hydrogen in orthonitrobrombenzene by 

 n and x {x= position of (NO^)), 



and in metanitrobrombenzene by a and y (»/=position of (NO.^)), 

 then the replaced atoms of hydrogen in the dinitromonobrombenzene (melting- 

 point 72°) umst be represented by the letters o, x, y, and it may therefore be 

 called an ortho-nieta-dinitromonobrombenzene. 



On the Continuous Production of Oxygen. By J. Alfred Wanklyn, F.C.S. 



Tessi^ du Mothay has worked successfully a process by which oxygen is with- 

 drawn from the atmosphere and subsequently liberated in a state of purity. His 

 process consists in exposing manganate of soda to the alternate action of steam and 

 air at a low red heat. 



By the action of steam on the manganate of soda, oxygen is set free, a certain 

 quantity of the manganate being decomposed. By the action of air the decom- 

 posed permanganate is reproduced, and is ready to be acted upon afresh by steam. 



Commercially the process is a success. There is a point of great chemical 

 interest in the process. The steam is actually taken up in the operation and forms 

 caustic soda ; and it is highly probable that the following is a true representation of 

 the chemical changes which take place : — 



(MnO,)" (NaO),+H.,0=H,(NaO)2+Mn03-fO, 

 II,(Nab),+Mn62-|-d=(MNO„)"(NaO)o+Hp. 



On some Neiu Methods of Analyzing the Ethers. 

 By J. Alfred Wankltn, F.C.S. 



It is well known that the proportion of acid derivable from an ether when it is 

 decomposed by means of alkali, may be determined with great precision. For 

 example, the acetic acid yielded by acetic ether may be titrated with accuracy. 

 The author proposes to determine the proportion of .alcohol obtainable when an 

 ether is decomposed by means of alkali. Tlie method consists in digesting a 

 weighed quantity of the ether with excess of potash or baryta, and, when the 

 decomposition is complete, in adding water, distilling off the dilute alcohol, and 

 weighing the distillate, and taking its specific gravity. There is no objection 

 to the addition of a weighed quantity of alcohol in order to facilitate the de- 



