128 Dr Davy's Miscellaneous Chemical Observations. 



rather below its average li^ight, one-third may be added to this 

 result; and we have about 1,200,000,000 or twelve hundred 

 millions of tdns per annum. As extreme accuracy in such com- 

 putations, unless made daily throughout the year, is not to be 

 expected, our conclusion can only be looked upon as a tolerably 

 close approximation to the truth. 



We have also made several barometric measurements of the 

 height of Arthur's Seat in a variety of weather, as well as of 

 some of the highest of the Pentlands, but the length to which 

 this article has already extended prevents us from discussing 

 them for the present. 



Edinburgh 

 Nw, 1828, 



"'} 



• Miscellaiieous Chemical Observations. By John Davy, M. D. 

 F. R. S. Physician to the Forces. Communicated by Sir 

 James Macgrigor, Director-General of the Army Medi- 

 cal Department *. 



1. Effects of Light on Sohiiion of Tartar Emetic and Antimonial 



Wine. 



When a solution of tartarite of antimony and potash is ex- 

 posed for some weeks to the direct rays of the sun, in a close 

 vessel, it is rendered turbid, and a precipitate forms, which has 

 ;the properties of the protoxide of antimony. In one instance, 

 , that a drachm of tartar emetic, dissolved in four ounces of dis- 

 tilled water, was exposed to sunshine at Corfu and Malta, du- 

 ring twelve months, the precipitate collected weighed one grain, 

 and consisted of peroxide as well as protoxide of antimony. 

 The decomposition, from the action of the sun's rays, takes 

 place very slowly at first, till the solution has become turbid, 

 and then the change is greatly accelerated. This probably is 

 owing to the particles of oxide of antimony disengaged exert- 

 ing an influence on the others similar to what is witnessed in the 

 experiment of the precipitation from an acid solution of one 

 metal by another. 



It might, perhaps, be expected, that antimonial wine would 



• I have prefixed titles to the different articles— Edit. 



