98 Dr. Ure on Opium and its Tests, 



present ; for the previous dilution with water has been so great 

 as to remove the inequalities of colour in the original spiri- 

 tuous solutions. Let the darker shades be now lightened with 

 water till the tints of the whole be uniform ; and the relative 

 volumes of the liquids will afford an approximate measure of 

 the qualities of the several opiums. It is obvious that a double 

 quantity of any given opium will take a double volume of water 

 to bring its meconate of iron to the standard shade. By this 

 means different tinctures of opium may be very expeditiously 

 compared in narcotic power. 



I have tried in this ready way Turkey, English, and East 

 Indian opium, and have found the results to harmonize suffici- 

 ently with their known powers determined by other methods. 

 An improved East Indian opium, of which Dr. Chambers gave 

 me a specimen, approaches by this test very closely to the 

 quality of fine Turkey opium. 



The employment of red muriate of iron as a re-agent for de- 

 tecting the meconic acid of opium has been frequently resorted 

 to, under different modifications, since Vogel first pointed out 

 the singular sensibility of that acid to the peroxide ferreous 

 salts. I have found solution of acetate of lead, faintly acidu- 

 lated with vinegar, the preferable re-agent for separating meco- 

 nic acid, in the form of a meconate of lead, from solution of 

 opium. The slight excess of acetic acid prevents any of the 

 morphia from falling down with the oxide of lead. Twenty- 

 seven grains of washed, but still impure meconate of lead, may 

 be obtained from one hundred grains of good opium — a result 

 which I obtained both from the Turkey and the above East 

 Indian. By treating this insoluble salt, diffused in water, with 

 the equivalent quantity of sulphuric acid, or by a stream of 

 sulphuretted hydrogen gas, the meconic acid is set free, and 

 may be procured in small crystalline grains by slow evapora- 

 tion of the filtered liquid. These grains, once concreted, are 

 very difficult of solution in water, and may therefore be washed 

 with this fluid. Of the washed grey-white grains, a solution 

 perfectly colourless strikes a deep brown-red with a drop of 

 permuriate of iron. 



Another process for procuring meconic acid has been pre- 

 scribed. The magma obtained by boiling magnesia in a 

 watery infusion of opium, is to be washed first with proof 



