50 Dr. T. Thomson on Pyroxylic Spirit and its Compounds. 



end, the rest of the phosphorus is added, and the whole agi- 

 tated. By and by heat must be applied, otherwise the effer- 

 vescence would cease altogether. The distillation is continued 

 as long as an aethereal liquid continues to pass. 



The residue in the retort contains phosphorous acid, phos- 

 phomethylic acid, and phosphorus. It is quite deprived of 

 colour. The liquid in the receiver is composed of pyroxylic 

 acid and iodide of methylene. When water is added to the 

 mixture the iodide immediately separates. The quantity 

 obtained nearly equals the weight of the iodine employed. 

 It is still very impure. To obtain it in a state of purity, we 

 must distil it over the water-bath with chloride of calcium, 

 and litharge in great excess. 



It is a colourless liquid, weakly combustible, burning only 

 when put into the flame of a lamp, and then giving out violet 

 vapours in great abundance. Its specific gravity at 71° is 

 2'237. It boils when heated to between 100° and 120°. 



Dumas and Peligot analyzed it by means of oxide of cop- 

 per, and obtained 



Carbon 8*92 or 2 atoms = 1*5 or per cent. 8*51 



Hydrogen 2*23 or 3 atoms = 0-375 — — 2*12 

 Iodine 88*85 or 1 atom = 15-75 — — 89-37 



100-00 17-625 100 



or C^ H^ lod. 



Dumas and Peligot found the specific gravity of the va- 

 pour of iodide of methylene 4-883. This specific gravity would 

 indicate 1 volume carbon 0-4166 



2 vojumes hydrogen 0-1388 



1 volume iodine vapour 8-8000 



2)9-3555 



4-6777 

 condensed into 2 volumes. It is obvious that there is an 

 error in determining the composition of the iodide, or in that 

 of the specific gravity of the vapour. 



3. Fluoride or filiate of methylene. — This compound was 

 obtained by Dumas and Peligot* in the following manner: 



A mixture of fluet of potassium and sulphate of methylene 

 was gently heated in a glass vessel. Sulphate of potash was 

 formed, and a gas escaped, which being collected over water, 

 was pure, and constituted fluate of methylene. 



It is colourless, has an aethereal smell, and burns with a 

 flame, similar to that of alcohol, only a little more mixed 

 * Ann. de Chim. et de Phys. Ixi. 193. 



