1815.] i'fi the Physical Sciences. 17 



contact with oxygen or chlorine gases. 3. Electricity causes it to 

 expand, and throws down the greatest part of the potassium. 

 4. Though kept in contact with water, it does not lose the whole, 

 but only apart, of its potassium. Hence Sementini concludes that 

 hydrogen lias the property of combining with two proportions of 

 potassium. 



9. Nilrotts Oxide. — From the experiments of Professor PfafT, of 

 Kiel, it appears that when the nitrate of ammonia employed to 

 prepare this gas contains sal ammoniac, as is commonly ihe case, 

 the G:as which comes over is the same as that noticed by Proust and 

 Vauquelin, which has a peculiar taste and odour, and acts with 

 violence upon the lungs. Hence the method of preventing the 

 occurrence of this foreign gas Is obvioiis. 



9. Sulphureled Azotic Gas. — A controversy has been carried on 

 in Germany for some years respecting the existence of this gas. It 

 was first announced by Gimbernat as existing in the mineral waters 

 of Aix-la-Chapelle. Then appeared the analysis of these waters by 

 Dr. Reaumont, and by Messrs. Monheim and Lausherg ; the expe- 

 riments of Westrumb on the same subject ; and tiie attempts of 

 Berzelius a-nd Hedenbcrg to form sulphurctcd azotic gas artificially, 

 which were not attended with success. I do not con^^ider it as 

 necessary to enter into the particulars of this controversy, i shall 

 merely state what I conceive to be the result of it. No person has 

 ever succeeded in forming sulphureted azotic gas artificially. The 

 waters of Aix-la-Chapcllc seem to contain both azotic gas and sul- 

 phureted hydrogen gas. The sulphureted azotic gas of Gimbernat 

 seems to have been nothing else than a mixture of these two gases. 



IV. Metah. 



The most indefatigable experimenter of late years on the metallic 

 oxides is Professor Berzelius. For the greater part of his results I 

 must refer to his dissertation On the Cause of Chemical Proportions, 

 published in the third volume of the Annals of Philo'^npliij, where 

 almost the whole of his results will be found ; hut as the details of 

 the experiments are frequently omitted in that dissertation, and as 

 I am aware, from conveisations which 1 have had on the subject 

 with different young chemists, that some o\' these details would he 

 very acceptable, 1 shall take the present opportunity of stating some 

 of tliose which seem most important in this place. 



1. Oxides of Gold. — The facility with which gold parts with its 

 oxygen is well known, and every chemist is aware of the impos- 

 sibility of obtaining the oxides of this met;'! iu \ state of purity. 

 Berzelius' method of estimating the quantity of oxygen in the per- 

 oxide of gold, which alone can be suhjccted to direct examination, 

 was very simple and ingenious, but re(|uired considerahle dexterity. 

 He dissolved a given (juantity of gold in aqua regia, evaporated tht; 

 solution gently to dryness, to get rid of the excess of acid, and then 

 redissolved the salt in water. He now ascertained, with rigid accu- 

 racy, how much mercury was necessary to precipitate tlie gold in 



Vol. V. N" I. B 



