236 ANNUAL OF SCIENTIFIC DISCOVERY. 



NEW METHOD OF DECOMPOSING SILICATES. 



A NEW method of decomposing silicates in the process of analysis 

 has been announced by Mr. Henry Wurtz, of New York. It consists 

 in the employment as a flux, in the decomposition of the silicates by 

 fusion, of the chlorides of several of the alkaline earths, as the chlorides 

 of barium, strontium, and calcium, the two former being preferable. 

 Felspars and hornblendes, on fusing with these substances, are readily 

 decomposed on treating with hydrochloric acid. The method appears 

 to possess many advantages, for decomposing silicates which contain 

 both the alkalies, over the ordinary methods of fusion with hydrate 

 or with carbonate of barvta. Silliman's Journal. 



ON A PECULIAR COMPOUND OF LARD AND ROSIN. 



AT the meeting of the American Association, at New Haven, Pro- 

 fessor Olmsted read a paper on some peculiar properties possessed by 

 a compound formed of hog's lard and common rosin. He says, " An 

 accident first led me to observe something remarkable in this com- 

 pound. Wishing to fit the brass plate of an old air-pump so as to 

 make a close joint with the receiver, I had been accustomed to apply 

 to the plate a disk of leather, saturated with lard. With the hope of 

 rendering it more completely impenetrable to air, I added to the lard 

 a small quantity of rosin, and melted them together. I expected the 

 rosin would give greater hardness to the lard, and make it fill the 

 pores of the leather more effectually, but was surprised to find that 

 the change produced by the rosin was to impart to the lard a tendency 

 to remain in the fluid state, so that, in a winter's day, the compound, 

 when cold, remained in the state of a semi-fluid, at the temperature 

 of a room moderately heated. I found, also, that this preparation, 

 when applied to the leather of the air-pump, rendered it peculiarly 

 soft, and, at the same time, very impermeable to air, so as to form a 

 good joint with the receiver. But what more particularly arrested my 

 attention was this, that, having inadvertently left the leather on the 

 plate of the pump for nearly a year, during which time the use of the 

 apparatus was discontinued, I supposed, when I took it out again, 

 that I should find the brass plate much corroded, as I had sometimes 

 seen it before, when exposed for a much less time to the action of the 

 oiled disk of leather; but, on the contrary, the brass was entirely free 

 from corrosion, and I have uniformly found the same to be the case 

 since, however long the leather may have remained in contact with 

 the plate. This observation suggested another and more important 

 use of the same preparation for lubricating the pistons, which, being 

 likewise of brass, and moving in brass barrels, had before occasioned 

 me much inconvenience, by their liability to corrode by the action of 

 the oil used for lubricating on the brass. 



" I have recently made a few experiments, with the view of ascer- 

 taining the melting point of this compound, and the proportions of the 

 ingredients which give the lowest melting point. The best propor- 

 tions are, by weight, lard threo parts, rosin one part. If the rosin 



