PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 609 



should be regarded, however, as a conditional structure, only to remain 

 nntil the true foundations of the science are laid, by the broader generali- 

 zations of some future Gauss. It may be suggested in this connection that 

 the implied coexistence of several distinct "ethers," as the mediums of the 

 forces of light, heat, actinism, magnetism, and electricity, is quite as ob- 

 jectionable as the corpuscular hypothesis. May not all these manifesta- 

 tions arise from the varying density, and diverse motions of the same elas. 

 tic, subtle, all-permeating, all-pervading " cei/i," which fills the interstellar 

 spaces, and in a more compact state, envelopes both atom and orb ? 



Decomposition of Iodide of Mercury. 



H. Rose, in Poggendorjf's Annalen, states that Iodide of mercury is easily 

 decomposed by cyanide of potassium. To estimate the amount of mercury 

 in the iodide, the cyanide of potassium is first rubbed in a mortar, with 

 twice its weight of quicklime. A little carbonate of magnesia is then plac- 

 ed in a tube, closed at one end; the iodide is mixed with eight or ten times 

 its weight of cyanide, a layer of lime is next introduced, then a layer of 

 cyanide, and lastly, carbonate of magnesia is placed on the top; the tube is 

 now drawn out and bent, its extremity being made to dip into a receiver 

 containing water. Heat is now applied to the mixture beginning at the 

 top, and the mercury distils over. 



Other mercurial compounds may be decomposed in the same manner. 



According to Carius, iodide of mercury is completely decomposed by di- 

 gestion with nitrate of silver, not very acid. Iodide of silver, like iodide 

 of mercury, is slightly soluble in nitrate of mercury. 



The red iodide of mercury may be reduced by a solution of proto-chlo- 

 ride of tin, when hydrochloric acid is added, and the mixture is supersatu- 

 rated with it, metallic zinc completely decomposes iodide of mercury in the 

 presence of water forming iodide of zinc. 



Purification of Sulphuric Acid. 



F. M. Lyle, gives in The London Chemical News the method practiced by 

 him. If the acid contains nitrous compounds it is heated in a porcelain 

 capsule, to about 110 deg. C, with a small portion, one-quarter to one-half 

 percent of oxalic acid, previously added, till the latter is decomposed and 

 effervescence has ceased. The acid is then allowed to cool down to about 100 

 deg. C, and bichromate of potash, in fine powder, or in solution with sul- 

 phuric acid, is then added until the green color first produced by the for- 

 mation of sesquioxide of chromium is replaced by a yellowish green, indicat- 

 ing a mixture of chromic acid in a free state. The acid so prepared, being 

 now distilled, passes from the first perfectly free from all impurities. 



On the Secular Cooling of the Earth. 



The Rev. Prof. Haughton, of Trinity College, Dublin, in a paper read be- 

 fore the Dublin Geographical Society, expi-essed his belief that the time 

 during which organic life has existed on the earth is practically infinite 

 because it can be shown to be so great as to be inconceivable by beings of 

 our limited intelligence. The commencement of organic life on the globe 

 [Am. Inst.] N* 



