222 Professors Redtenbacher and Liebig 



hind, from which the carbon cannot be expelled by subse- 

 quent calcination. It is true, the carbon burns at the surface 

 of the carburet, leaving a stratum of pure silver, but this pro- 

 tects the inner part from the contact of oxygen ; and when 

 this residue is dissolved in dilute nitric acid, a net-work of 

 pure carbon remains. 



The behaviour of the benzoate of silver is very similar to 

 that of the cyanide ; it is easily obtained perfectly pure, in 

 beautiful shining crystals, which are not hygroscopic ; when 

 this salt, to the amount of 7 to 12 grammes, is heated, it melts 

 and is decomposed ; but even after being kept at a red heat 

 for twelve hours, a very considerable quantity of carbon is 

 found in the residue of silver. 



The oxalate of silver appeared at first to be the most appli- 

 cable of any in these determinations, but it is almost impos- 

 sible to obtain it anhydrous, besides which, when heated in 

 large masses, it deflagrates in the same manner as the fulmi- 

 nating mercury. We could, it is true, ascertain its compo- 

 sition by decomposing it, by means of hydrochloric acid, but 

 we consider it important to bring no foreign element into 

 these determinations. In the following experiments, the 

 acetate, the tartrate, the racemate, and the malate of silver 

 were employed. 



Acetic acid, owing to its volatility, is easily obtained quite 

 pure. We prepared it by decomposing some brilliantly 

 white sugar of lead, which had been frequently recrystallized, 

 in the usual manner, by means of sulphuric acid. The acetic 

 acid thus obtained, which was free from sulphurous acid, was 

 once more rectified over binoxide of manganese in excess. 

 The pure acid was then partly saturated with ammonia, and 

 precipitated by nitrate of silver in the warm. A shining 

 white precipitate was obtained, possessing the form of small 

 laminae, having a silvery lustre; this was perfectly washed on 

 a filter, dissolved in hot water, the solution filtered, and left to 

 cool in a glass vessel, when at the bottom, at the surface, and 

 on the sides, broad shining needles of acetate of silver, of an 

 inch in length, were formed ; these were again washed with 

 pure water, dried in the air, finely powdered in an agate 

 mortar, and exposed to a stream of dry air at 103° C, until 

 the weight remained unaltered. 



In each individual analysis, the weighed salt was once more 

 heated in a water-bath for an hour, and then allowed to cool 

 under a bell-glass with concentrated sulphuric acid; after 

 which it was again weighed. It never occurred in our expe- 

 riments, that the weight was perceptibly altered by this treat- 

 ment ; this precaution was nevertheless uniformly adopted. 



