110 /. IF. Langley on Detection of Picrotoxine. 



remove the organic base by ether from an aqueous solution, while 

 the same course pursued with picrotoxine would fail to remove 

 any of it from the water, it being positively necessary that the 

 solution should be neutral or acid to enable the ether to dis- 



Picrotoxine is soluble in one hundred and fifty parts of cold 

 water, but if a small quantity of caustic alkali is present it will 

 readily dissolve in six or eight times its volume. When this 

 solution is gently heated it becomes yellow and on platinum foil 

 at a temperature far below ignition assumes a brick-red color 

 which is distinctive and quite unlike the shade produced by sugar 

 under similar circumstances. Picrotoxine like sugar and many 

 indifferent organic bodies, possesses the property of reducing 

 certain metallic oxyds. "It changes bichromate of potass to a 

 fine green color." (Gmelin.) "An alkaline solution of picrotox- 

 ine reduces sulphate of copper to the suboxyd. (Otto.) This 

 property however is common to too many other substances to be 

 at all distinctive. A far more reliable test is found in oxydation. 



If dry picrotoxine and nitrate of potassa are rubbed together 

 in a watch-glass and a drop of sulphuric acid is added, no pe^ 

 ceptible change occurs, but if a strong solution of caustic soda 

 or potassa is poured upon this a bright reddish-yellow color is 

 communicated to the mixture which partially dissolves and causes 

 the whole liquid to assume the same tint. In this way very 

 minute traces of picrotoxine may be discovered, so small a quan- 

 tity as j^Vo of a gramme, if pure, being detected with the great- 

 est ease. When as small a quantity as this is used we see the 

 color most distinctly by gently breaking the solid cake of sul- 

 phate of potassa which lies on the bottom of the dish ; portions 

 of the precipitate will then appear of a crimson or purple hue. 



In applying this test it is best to add about thr^ or four : 

 the quantity of nitrate of potash that we have of substaiK . 

 examined and to use no more sulphuric acid than is ne 

 to moisten the mass. The solution of potassa or soda sbu ^ 

 made very strong and enough added to ensure considerable ^-^ 

 linity in the mixture after the neutralization of the sulphuric 

 acid. 



Other powerful oxydizing agents will produce the same resrn* 

 but not with equal facility ; chlorine passed over the moistened 

 crystals, slowly dissolves them, and if we pour the aiK 

 solution upon them we obtain the same color, or we ma}- 

 tute chlorate of potassa for the nitrate, the objection to " 

 of this however will be found in its tendency to explou- 

 coming in contact with the acid. 



This color, however produced, is not permanent but will slowly 

 disappear with a rapidity proportioned to the amount of substance 

 taken, but it will always appear with great distinctness whe^^ 

 first adding the alkaline solution if any picrotoxine is present. 



