CHEMICAL TOXICOLOGY 281 



a good plan to allow the distillate to drop on to a small 

 filter and collect the clear liquid in a flask or test-tube. 

 Phenols (carbolic acid and creosote), turpentines (savin), 

 essentials oils (camphor, etc.), and chloroform in fairly 

 large proportions, form a distinct fluid turbidity or emulsion, 

 and may actually separate into distinct oily drops, -whilst 

 camphor is solid. Phosphorus forms semi-solid globules, 

 a'nd the other substances named are soluble. 



Phosphorus, creosotes, turpentine, and some essential 

 oils, distil slowly, and a large bulk of liquid must be distilled 

 in order to efifect a complete separation. The other com- 

 pounds — viz., hydrocyanic acid, alcohol, ether, chloroform, 

 and the :gases sulphuretted hydrogen and sulphur dioxide, 

 being very volatile, concentrate in the first portions of 

 distillate. If a large volume is collected, the dilution may 

 be so great as to seriously interfere with the qualitative tests 

 (especially with hydrocyanic acid), and it is therefore wise 

 to stop the distillation after about 5 c.c. of clear distillate 

 has been obtained. Small portions are then separately 

 tested for the substances in question — e.g., by the Prussian 

 blue test for hydrocyanic acid, by the iodoform test for 

 alcohol, by the neutral ferric chloride test for phenols 

 (carbolic acid purple, creosote smoky colour), or bromine 

 water for phenols (solid tribromphenol from carbolic acid, 

 resinous bromcresols from creosote). 



In order to effect a partial separation and purification of 

 the volatile substances obtained at this stage the distillate 

 is made alkaline with sodium hydroxide (not carbonate) 

 and redistilled. Turpentines, essential oils, alcohol, ether, 

 and chloroform (also given from chloral by alkali) distil 

 over. If the alkaline liquid is now made acid with dilute 

 sulphuric acid and again distilled, hydrocyanic acid, 

 phenols, sulphuretted hydrogen, and sulphur dioxide pass 

 over. In the course of these manipulations traces of 

 phosphorus suffer oxidation, whilst with alkali on heating 

 phosphuretted hydrogen and hypophosphorous acid are 

 formed. 



Having distilled from acid solution, the original residue in 



