58 Ou the Cause of Chemical Proportions. [Jan. 



more than twice as much oxygen as the base by which it is neu- 

 tralized. Hence it ought to contain 73' 18 per cent, of oxygen, 

 which coincides sufficiently with the experiment of Davy. If, on 

 the other hand, we calculate the composition of boracid acid from 

 the quantity of water contained in tlie crystallized acid, the pro- 

 portion of oMvgen will amount only to 69-4 per cent. 



3. I endeavoured to verify the preceding determination by other 

 analyses ; as for example, by analyzing borate of lead and borate 

 of barytes ; but I did not obtain satisfactory results. Borate of 

 lead yielded, in diiferent experiments, from 1 HJ to 118 per cent of 

 sulphate of lead ; but the liquid from which this had been preci- 

 pitated still contained lead, and I was not able to determine exactly 

 how raucii. The result was still less satisfactory when I precipi- 

 tated a given weight of nitrate of lead by borate of ammonia, 

 because the borate of lead formed is soluble in the water employed 

 to wash it. Borate of barytes presents difficulties still greater, 

 because boracic acid forms several compounds with barytes, all of 

 which contain more acid in proportion than the alkaline borates by 

 means of which they are formed. These borates are more or less 

 soluble in water, and in these solutions carbonic acid decomposes 

 them, precipitating carbonate of barytes. Borate of barytes formed 

 by precipitating muriate of barytes by means of borate of ammonia, 

 and well washed, was deprived of its combined water by exposure 

 to heat : 100 parts of this borate dissolved in nitric acid, and de- 

 composed by sulphuric acid, produced 63"92 parts of sulphate of 

 barytes, equivalent to 41 '93 of barytes; that is to say, that 100 

 parts of boracic acid had been combined with 7-'^ parts of barytee. 

 If we consider the borate of ammonia as neutral, this borate of 

 barytes is a superborate in which the acid contains 10 times as much 

 oxygen as the base ; that is to say, in which the base is combined 

 with five times as much acid as in the neutral borate. By analysing 

 in the same way the precipitate obtained from muriate of barytes 

 by common borax, 1 obtained from 100 parts of calcined borate of 

 barytes 85 parts of sulphate of barytes. In this borate 100 parts of 

 acid are united with 126 parts of barytes; that is to say, that the 

 acid ought to contain six times as much oxygen as the base. The 

 base, of course, is combined with three times as much acid as in 

 the neutral borate. These two borates are soluble in water; but 

 the second is much more so than the first. Boiling water dissolves 

 little more than cold water; and the small surplus falls in the state 

 of a white powder without any appearance of crystallization : even 

 when the liquid is evaporated no crystals are formed ; and if the 

 evaporation be performed in an open vessel, flocks fall which consist 

 partly of carbonate, partly of borate of barytes. I thought it worth 

 while to relate these experiments, in order to show the difficulty of 

 controlling the result of the analysis of borate of ammonia, and to 

 make known some of these borates, hitherto scarcely examined. 



From the preceding experiments, I conceive we may conclude 



