Full text: Vol. II (2)

72 EXPERIMENTS OF MARGRAAF AND JAQUIN. 
which, at the fame time, were quite inconsistent with the common 
opinion. It is well known, that when a calcareous ſtone or maſs is 
burnt to quicklime, it does not acquire any additional weight in the 
fire ; but, on the contrary, fuffers a very great loss. The lime, when 
fresh drawn from the furnace, weighs generally no more than 60 per 
cent. of the weight of the limestone; and when I considered some ex 
periments made some time before by Mr. Margraaf of Berlin, it ap 
peared plain that the matter separated from the limestone by heat, 
is an elastic aërial matter, incapable of being condensed by cold into a 
palpable form. These experiments are described in the Tranfactions 
of the Berlin Academy for 1748, and were made upon a particular 
calcareous substance of which he had undertaken the examination : It 
is called ofteocolla. He put eight ounces of osteocolla, which is a cal 
careous earth, into an earthen retort, to which he joined a receiver, 
and set the retort in a proper furnace, where it was gradually heated 
to a violent degree. Nothing, however, was condensed in the receiver, 
except two drachms of water, which, by its ſmell and properties, ſhew 
ed itself to be flightly alkaline. He does not tell us the weight of the 
oſteocolla remaining in the retort : He only fays that it was convert 
ed into quicklime ; but this alone, and the heat he applied, are suffi 
cient proofs that it had lost about three ounces of its weight ; and as 
no more than the quarter of an ounce of water was found in the re 
ceiver, it is plain that this loſs was occafioned chieffy by the separa 
tion of an elastic aërial matter which could not be condensed. 
The ſame thing has fince been more fully ascertained by Professor 
Jaquin of Vienna. In order to satisfy himself of the truth of my 
theory, he put a quantity of limestone, broken down to ſmall pieces, 
into an earthen retort, and fet it in a furnace, in which it might be 
heated to a violent degree. A receiver, with a very small hole drilled 
in the bottom of it, was luted to the retort, perfectly air-tight : Then 
fire was applied, and heat raised in a flow and regular manner. 
1/, A very small quantity of water was condensed in the receiver.
	        
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