VOL. LXXXVIII.] PHILOSOPHICAL TRANSACTIONS. 26l 



as well as on account of its affording a soap-like matter with caustic soda, this pre- 

 cipitate may be considered as a species of animal matter ; and, from its composition 

 being analogous to that of the substances called, in the new system of chemistry, 

 animal oxides, it belongs to that genus. Its peculiar and specific distinguishing 

 properties are, imputrescibility, facility of crystallization, insolubility in cold 

 water, and that most remarkable property of all others, producing a pink or red 

 matter, on evaporation of its solution in nitric acid.* 



Having found the above precipitate to be an oxide, and not, as is commonly 

 supposed, an acid, I thought it probable that, like other analogous oxides, it was 

 acidifiable, and I suspected that I had really rendered it into the acid state, by the 

 nitric acid; which, in the above experiments, (e, 14), had imparted oxygen to it, 

 and so rendered it soluble, deliquescent, pungent, and volatile. This change 

 also would account for the nitric solution not affording the precipitate. In order 

 to obtain, for examination, an adequate quantity of this supposed acid, the follow- 

 ing experiments were instituted, with the 3 acids, viz. the oxymuriatic, the nitro- 

 muriatic, and the nitric, which can acidify oxides analogous to the present one. 



Exper. ] . Twenty-five grains of the above animal oxide, (for so I will now ven- 

 ture to call it), and 3 oz. of nitric acid, of the specific gravity of 1.25, were put 

 into a retort, and the hydro-pneumatic apparatus was adjoined. At a very low 

 temperature, a clear solution was made. 1. Soon after the solution began to boil, 

 23 oz., by measure, of colourless gaz came over, which were succeeded, 2, 

 by white fumes, filling the apparatus, and 23 oz. more of gaz. 3. A white 

 sublimate ascended, and there was a strong smell of prussic acid. The sublimate 

 was very readily washed out, being very soluble, and tasted pungent or sharp, but 

 not sour. 4. The distillation being renewed, more white sublimate appeared, but 

 only 3 oz. more of gaz came over; and then the retort only contained a dark-brown 

 solid matter. The first portion of gaz, viz. 23 oz., consisted of about equal bulks 

 of carbonic acid and atmospherical air. The 2d portion, viz. 23 oz., was -§- of its 

 bulk carbonic acid, and the rest nitrogen gaz. The 3d portion, or 3 oz., was 

 atmospherical air, with a little carbonic acid. 



Nitric acid was poured, in the same quantity as before, into the retort. An 

 effervescence immediately took place, which was succeeded by a transparent solu- 

 tion. The distillation yielded gaz of the same kind as before, but in smaller 

 quantity, with white fumes, and white sublimate. When only about 4 dr., by 

 measure, of liquid remained in the retort, a little of it was evaporated; and, when 

 reduced to a solid matter, it turned black, and took fire, leaving a carbonaceous 

 residue; but, before this, a margin of beautiful pink matter appeared. 



* It is much to be wished that we possessed equally delicate tests of the other species of animal 

 matter, which are confounded together, though, from their obvious properties, there is reason to be- 

 lieve that they are of very different kinds, as is the case with the matter of the brain, liver, voluntary 

 muscles, mucus, &c. Mr. Hunter has discovered a distinguishing specific property of pus, and one is 

 here indicated for the oxide of urinary concretions. — Orig. 



