1835.] First Astronomer- Roy aL 425 



ing the lunar theory and tables, did it to oblige his friend- 

 ship, who had then a great interest in a great courtier : 

 and considering also that [they] were persons of very ordi- 

 nary skill in that part of mathematics which was concerned 

 with the heavens and the lunar theory. 

 ( To he continued.) 



Article II. 



Mesearches into the Nature of the Decolourizing Combinations 



of Chlorine. By A. J. Balard. 



C Concluded from p. 35 1. J 



Composition of Chlorous Acid. 

 The experiments which have been detailed prove that 

 chlorous acid consists of chlorine and oxygen, but they do 

 not determine the proportions in which these elements are 

 united. Further researches were necessary for this purpose. 

 Several methods of analyzing chlorous acid diluted with 

 water present themselves. It may, for example, be decom- 

 posed by a combustible, which will liberate the chlorine ; 

 when the proportion of this gas and the oxygen combined 

 with it may be determined ; or the acid may be treated by 

 metallic silver, and the products of oxygen and chloride of 

 silver collected. But, by each of these methods, only one 

 of the elements of the acid is procured in a gaseous state. 

 It is necessary to determine the volume of the other by 

 weighing and calculation which renders the analytical pro- 

 cess very tedious. It was necessary, therefore, to endeavour 

 to fall upon a method by which the elements would be 

 obtained in the form of a gaseous mixture. The action 

 which chlorous acid exercises upon oxalic acid appeared to 

 present an easy process. We know that oxalic acid, when 

 decomposed, is resolved into carbonic acid and carbonic 

 oxide, and that this last compound requires the half of its 

 volume of oxygen to change it into a volume of carbonic 

 acid equal to its own. Hence, it results that when oxalic 

 acid is converted into carbonic acid gas, the fourth of the 

 gas obtained represents that of the additional oxygen which 

 was required to produce this change. 

 The analysis of chlorous acid is thus resolved into the 



