1820.] Pht/sical Science during the Year 1819. 97 



12. Pink Sediment in Urine. — It appears from an analysis of 

 this substance by Dr. Prout that it consisted chiefly of urate of 

 ammonia. What is called the lateritious sediment in urine is 

 usually a mixture of phosphate of lime and of magnesia witii 

 urate of soda. The red colour is usually owing to the presence 

 of purpurate of ammonia, or soda. Dr. Prout informs us that ho 

 has detected nitric acid in such sediments. The following was 

 the method he adopted : The sediment was digested with a little 

 pure barytes. The nitrate of barytes thus formed was of course 

 soluble, while the other compounds were insoluble. Sulphate of 

 potash was now added to the solution of nitrate of barytes, and 

 the nitrate of potash thus formed was obtained on evaporating 

 the solution in one instance in crystals, and in several others its 

 presence was rendered distinctly perceptible by its mode of cor«- 

 bustion with paper and other substances containing carbo:i. 

 Some specimens of these sediments contained very little or no- 

 nitric acid. The specimen yielding the most was deposited from 

 the urine of a gouty patient labouring under a febrile attack. 

 (See Med. Chirurg. Trans, vol. ix. p. 481.) 



13. Urinary Calculi. — It seems sufficient to refer the read-er 

 to Dr. Heniy's excellent paper on urinary calculi which has been 

 inserted in the Annals of Philosopki/, xv. 107. 



14. The same reference may suffice respecting the extraordi- 

 nary statement of calculi from a dog possessing the chemical 

 properties of pearl. (See ibid. xv. 30Ci.) 



XIV. Minerals. 



1. Fibrous Prehnite.— This is the variety of prehnite which 

 occurs in the neighbourhood of Glasgow. Its specific gravity, 

 hardness, and chemical composition, differ from those of toliated 

 prehnite. Hence I think it ought to be ranked as a species 

 apart. I found the constituents of a specimen from the neigh- 

 bourhood of Paisley as follows : 



Silica 43-60 



Alumina 23-00 



Lime 22-33 



Oxide of iron 2-00 



Water 6-40 



Loss 2-67 



100-00 

 (Annals of Philosophy, xiv. 67.) 



2. Necronite. — This is a name given by Dr. Hayden to ;!, 

 mineral found by him in primitive limestone about 21 miles frotn 

 Baltimore. The name was imposed in consequence of the very 

 fetid smell by which the mineral is distinguished (from ve^/jo,). 

 Tlie description is too imperfect to enable us to form any accu- 

 rate idea of the mineral, or to be able to determine whether it be 



Vol. XVI. N° II. G 



