445 



Analysis of the Calcareous Ttiffa at Green Point. By 

 Mr. Tredgold, Cape Town. 



Sir, 



\Jn a Letter to Dr. Smith.] 



Cape Town, 14th October, 1829. 



In reply to your inquiry respecting the result of 

 my examination of a specimen of lime-stone, which was hand- 

 ed me by Mr. Nisbet in the month of August, 1828, I beg to 

 forward you the following statement of my experiments, Avhich 

 I have copied from a memorandum I made at that time. 



To one hundred grains of the stone reduced to powder, Sul- 

 phuric Acid was added, and afterwards diluted with water, 

 Carbonic Acid was expelled, and the mixture was then ex- 

 posed to a sufficient heat to evaporate the water and supera- 

 bundant Sulphuric Acid. The dried mass was pulverised, and 

 washed several times in warm water ; and to these washings, 

 when cold and filtered, Carbonate of Potass was added ; a small 

 precipitate was produced, which when collected and dried, 

 weighed four grains, and this I found to be Alumine. 



Having ascertained that tbe stone was chiefly Carbonate of 

 Lime, I bruised 100 grains of it, and immersed it in Njtiric 

 Acid, aud by this means 38 grains of Carbonic Acid was ex- 

 pelled, and 12 grains of earth of a siliceous nature left undis- 

 solved. 



Another 100 grains of it I calcined, and in this experiment 

 the loss was 42 grains, which, allowing four grains for water, 

 leaves 38 grains of Carbonic Acid expelled. 



I considered these experiments sufficient to enable me to 

 conclude that every 100 lbs. of the stone may contain, in- 

 cluding the small portion of water noticed in the last experi- 

 ment, about 84 lbs. of Carbonate of Lime. 

 4 lbs. of Aluminous earth. 

 12 lbs. of Siliceous earth. 



I am, Sir, 



Your most obedient Servant, 



J. H. Trjsdgold, 

 To A. Smith, Esq. M.D. 

 &c. &c. 



Cape Town. 



