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SELECTED ARTICLES. 
acid, and the sulpho-cyanates of potassa and soda, and also 
that saliva, in consequence probably of the sulpho-cyanate of 
potassa which it contains, decomposes iodic acid and produces 
with it and starch a blue precipitate, not distinguishable from 
that produced under similar circumstances by morphia. 
The importance of this discovery, in a medico-legal point 
of view, is considerable, since iodic acid is now relied on by 
many as a test for morphia. 
Mr. Thompson thinks the above method for preparing iodic 
acid is cheaper and safer than that of Sir Humphrey Davy, 
and that it affords a purer acid than that of Gay Lussac. He 
agrees with Davy in thinking, that Gay Lussac's acid is sul- 
pho-iodic and not iodic acid. — Ed. Med, and Surg. Journ. 
From Lond. and Ed. Phil. Mag. 
ART. XL— EXTRACT OF A LETTER FROM PROFESSOR 
CHRISTISON OF EDINBURGH TO M. ROBIQUET, ON GAM- 
BOGE AND SCAMMONY. 
I propose to send you a long memoir, upon the origin and 
composition of gummi gutta. I am aided by a most intelligent 
collaborator, or rather a collaboratress, who is the wife of 
a Colonel of Ceylon. My colleague, Dr. Graham, and myself 
have demonstrated that the gummi gutta of Ceylon (which 
never comes to Europe except to the curious as myself) is 
identical as regards its composition with the gummi gutta 
from Siam, which is found in commerce, and that the 
plant of Ceylon, which Murray of Gottingen declares, from 
Ihe manuscripts and dried plants of Koenig, should produce 
the true gamboge, and which he designates under the name of 
Stalagmites gambogioides, is not a correct deduction, al- 
though it be adopted by the Pharmacopoeias and Pharmacolo- 
gists, and that the gamboge of Ceylon is the product of the 
Garcinia morella of Decandolle, or the Mangostana mo- 
