70 REPORT— 1871. 



detection a great many tests liare lieen proposed, most of which, however, have 

 little interest for the forensic chemist, particularly as they depend on phenomena 

 which may also he produced hy other substances beside morphine. It is not in- 

 tended here to justify this assertion by a critical examination of all the tests for 

 morphine which are liable to the reproach mentioned; it will he sufficient to 

 signalize one of them, the iodic acid, as an example. The well-known property of 

 this acid, of being reduced by morphine, is certainly adapted to distinguish the 

 latter from other alkaloids, but is altogether insufficient to establish the nature of 

 morphine, because there are a great many other substances, partly of organic, partly 

 of inorganic origin, which likewise reduce iodic acid. Nevertheless I have foimd 

 that iodic acid, with the aid of the microscope, presents a sure means of charac- 

 terizing morphine perfectly, because the reaction between this alkaloid and the 

 above-mentioned test proceeds under such peculiar appearances that morphine 

 cannot be mistaken for any other substance. The process to be adopted for this 

 purpose is the following: — 



After the morphine (of which the smallest particle is sufficient) is placed on a 

 slip of glass and covered with a glass cover, as much water is added as will fill the 

 space between the slip and the cover and extend a little beyond the margin of the 

 latter. After the glass slip is put under the microscope and this is directed to the 

 morphine, a particle of iodic acid is put into the water at the margin of the covering 

 glass. In a few moments a great number of minute spherical yellow molecules, of 

 constantly equal diameter, are seen to move in a direction from the iodic acid to 

 the sides of the morphine, and soon form in its vicinity numerous colourless needle- 

 shaped crystals, mostly united so as to form tufts. For the observation of this 

 microscopic metamorphosis a magnifying-power of 300 linear would be the most 

 suitable ; when a more powerfid system of lenses is employed, the difference of the 

 focal distances of the morphine and the above-mentioned, molecules and crystals 

 readily becomes too great for the distinct observation of the whole simidtaneously. 

 Hence it is also advantageous to place under the covering glass the thinnest possible 

 ■fragment of morphine. 



I reserve for another place a more detailed communication on this subject. 



Experiments on Chemical Di/namics. 

 By J. H. Gladstone, F.R.S., and Alfred Teibe, F.C.S. 



The authors had recently communicated a paper to the Royal Society in which 

 they investigated somewhat minutely what takes place when a plate of one metal, 

 such as copper, is immersed in a solution of a salt of another metal, such as nitrate 

 of silver. They had shown that, while the silver was being deposited on the copper, 

 an actual passage of the nitric element towards the more positive metal occurs, 

 causing the formation of a dense solution of nitrate of copper inside the crystalline 

 deposit, and a consequent downward current, and at the same time an upward 

 cm-rent of almost pure water fi'om the tips of the crystals. They had shown, also, 

 that with solutions of different strengths the chemical action in a given period 

 (say ten minutes) is not in direct proportion to the strength ; but, creteris 2J(tribiis, 

 twice the strength gives thi-ee times the chemical decomposition. This augmenta- 

 tion had been attributed to an increased conduction of the stronger liquid. In the 

 present paper the authors exhibited these phenomena in a dissected form, and 

 carried the observations still further. 



Instead of the silver crystals being allowed to grow from the copper into the 

 nitrate-of-silver solution, two separate plates were taken, one of copper and the 

 other of silver. The copper plate was immersed in nitrate of copper, and the silver 

 plate in nitrate of silver, while the two metals were connected by a wire, and the 

 two liquids were connected by a porous cell. Silver ciystals were gradually formed 

 upon the silver plate, while the copper was dissolved ; and at the end of some 

 hours it was found that all the silver had been removed from solution, and that 

 the loss of the copper plate was almost exactly what might be calculated from 

 the amount of nitrate of silver originally placed in the other cell. The actual 

 numbers were — theoretical 0'412, actual 0-402. The copper nitrate was formed in 



