of the combinations of phosphorus. 
33 5 
I have no doubt that the acid which I used formerly was 
drier than the acid employed in this experiment, which will 
account for the difference of the result. Supposing a hydro- 
phosphorous acid could be procured, containing only the 
quantity of water sufficient to convert it into dry phosphoric 
acid, it would consist, as I have stated in my former paper 
on phosphorus, of four proportions of water, and four pro- 
portions of phosphorous acid. 
I have adopted throughout the whole of these calculations, 
the supposition that the hydrogen in water is to the oxygen 
as 2 to 15 ; and consequently I have taken the number 
representing oxygen as 15, which is extremely convenient, 
as the multiples are simple, 30, 45, 60, &c. Taking the 
proportion of phosphoric acid in phosphate of potassa, which 
may be deduced from the experiments, page 329, it appears 
more convenient to represent the proportional number, or 
equivalent of phosphorus, by 45, or 45.2, than by 22.5, or 
22.6, which gives facility in adopting either hypothesis of the 
composition of hypophosphorous acid. If it be supposed a 
simple compound of oxygen and phosphorus, the series of 
proportions in the acids of phosphorus will be 
Hypophosphorous acid, Phosphorus 45 Oxygen 15 
Phosphorous acid - 45 Oxygen 30 
Phosphoric acid - 45 Oxygen 60 
Phosphoric acid 2 proportions 210 
Phosphuretted hydrogen i prop. 53 
I shall conclude this paper by a few incidental observations 
on the compounds of phosphorus. 
M. Du long states that no phosphorous acid is formed when 
phosphorus is burnt in excess of oxygen or atmospheric air ; 
