on Phosphoric Acid. 17 
some of which materially differ from the above. In the 
85 Vor. of the An. de Chimie, page 328, Thenard deter- 
‘mines phosphorous acid (obtained by slow combustion) to 
be 100 phosphorous and 110 oxygen, and is led to infer 
phosphoric acid to be 100 phosphorus and 165 oxygen. 
Berzelius’ account of phosphoric acid and phosphate of 
lime, published in 1811, I have noticed above; but he has 
since published another (An. de Chimie, 2—1816) in which 
he assigns 100 phosphorus and 128 oxygen for phosphoric 
acid and 100 + 77 for phosphorous acid. Dr. Thomson in 
his Annals of Philos. for April 1816, has given an account 
of his own labours on this subject; he finds phosphoric 
acid 100 phosphorus 4+ 123 oxygen, and the phosphates 
of lime to be a most intricate class of salts, namely, 5 
atoms of acid united with 1, 2, 3, 4, 5 and 6 atoms of lime 
severally ; the common earth of bones is supposed to be 
6 atoms acid + 4 lime; and the pentaphosphate (5 + 1), 
is the superphosphate from bones by sulphuric acid. In an 
article on phosphuretted hydrogen in August of the same 
year Dr. Thomson finds phosphoric acid to be 100 phospho- 
rus and 133 oxygen. M. Dulong in the Memoires d’Ar- 
eueil, Tom. 3, finds 4 acids, namely ; 
Hypophosphorous 100 Ph. + 37.5 Oxy. 
Phosphorous —— +H — 
Phosphatic — +112.5 
Phosphoric — +125 
After duly considering all that is advanced by these wri- 
ters, I am still of opinion that phosphoric acid is constituted 
nearly of 100 phosphorous and 150 oxygen (the atom weigh- 
ing 23); and for this constitution I am supported by the 
authorities of Lavoisier and of Davy. In regard to the 
phosphates too, 1 have seen no sufficient reason for any 
alteration. 
VOL. III. € 
