1814.] On the Cause of Chemical Proportions. 



of 

 e 



— ..--_,-- ^ -- J ^.u^.u.v. uj iiic iiiiiije 



of a spirit lamp, it lost still 12-9 per cent., making the whole loss 

 35 per cent. The lid of the crucible exhibited traces of sublimed 

 boracic acid. — (/.) I mixed 10 parts of dry boracic acid in powder 

 with 40 jiarts of oxide of lead, which had been heated to redness 

 immediately bcfi)re On this mixture I poured water in a platinum 

 crucible. 1 evapoiated this water slowly to dryness, and repeated 

 this process three times. The mass, after being dried the fourth 

 time, was exi)osc(! to a heat sufficient to melt it. The glass thus 

 formed weighed 45*6 parts, iience the -40 parts of oxide of lead 

 had combined with 5-6 parts of boracic acid, and 4*4 parts of water 

 had been driven off". This is exactly twice as much as the boracic 

 acid lost by cxpo^^ure on the sand-batb. These experiments seem 

 to prove that boracic acid contains 2 proportions of water 1 of 

 which is water of crystallization, while the other is a base to the 

 acid. In a moderate heat it loses its water of crystallization but 

 the other portion remains. It appeai-s that by a still stronger' lieat 

 half the water which acts as a base is disengaged, Icavin.- for 

 residue a superburus h//driats, wiiich is entirely decomposed^in a 

 red heat. 



2. Borate nf Ammonia. — Ten. parts of borate of ammonia 

 crystallized and veiy pure, were dried, and put in the state of 

 powder into a small retort with four times its weight of pure lime I 

 adapted to tlie retort a small tubulated receiver filled with caustic 

 potash, and furnished with a glass tube to allow the ammoniacal gas 

 to escape. This tube, as well as the receiver, was filled with 

 caustic potash, and the whole was exactly weighed. I now heated 

 the retort till the whole of its contents was red-hot, and till the 

 disengagement of ammoniacal gas had entirely ceased. The 

 receiver and tube had gained S-J/^ parts of water, and the crucible 

 had losiG-20.'j piirts of its weight. Hence it follows that the lime 

 had retained ^•'i\)T> parts of boracic acid, and had disen"-aged H 03'> 

 pans of ammoniacal gas: therefore borate of ammonia is com- 

 posed of 



Boracic acid 37-9.j 



Amn)onIa 30*32 



Water of crystallization 31"73 



100-00 

 Now 30-32 of ammonia contain 13-88G of oxy<rei), and 31-73 

 of water contain 28 parts: but /.i-SHG x 2 = 27772; so that the 

 water of crystallization constitutes 2 proportions for I of ammonia. 

 According to the result of this experiment, 100 parts of acid are 

 combined with 7!> 81)5 parts of ammoLiii : and if, as I have 5,hown 

 in A former essay, ammonia contains 45-8 per cent, of oxygen, these 

 'i'.rs'jo contain 36-59 parts. Horacic acid, then, cannot contain 



C 



