54 F. F. Runge on the Products [Jan. 



Article VIII. 

 On Pittacal, a new dye-stvff, (Poggendorff's Annalen xxxi.) 



Pittacal (ttltto, and kciaaos) is a name which Reichen- 

 bach of Blassko has given to a substance which is obtained 

 from impure picamare, or from portions of the oil of beech- 

 tar, which are heavier than water. Dissolve them in spirits 

 and add a drop of barytes water. The colourless liquid 

 becomes immediately blue, and in five minutes assumes an 

 indigo shade. When tar-oil is mixed with potash-ley till 

 it acts, litmus is only slightly tinged acid, and the oil is 

 placed in a solution of barytes ; while the latter becomes 

 pale- red, the oil on coming in contact with the air, is 

 rendered blue, and in a few hours black. With dry hydrous 

 barytes also, the tar-oil deprived of its acid by potash, 

 assumes an indigo colour in the air ; and lime, magnesia, 

 potash, soda, ammonia, hydrous silica, give it a reddish 

 or yellow colour. The cause of these colours depends on 

 the presence of pittacal. 



Pittacal is a dry, hard, brittle, dark-blue dye, of the 

 appearance of indigo. It is destitute of smell and taste, 

 and is not altered by a moderate heat ; but in a high tem- 

 perature carbonizing without an ammonical smell. In a 

 pure state, it seems rather to be suspended than to dissolve 

 in water. When well filtered, after some days, dark violet 

 flocks separate, and the solution is then completely colour- 

 less. Litmus, turmeric, light and air have no effect upon 

 it. Dilute acids, with the exception of nitric acid dissolve 

 it; sulphuric acid producing a violet-blue, or carmine 

 colour ; muriatic acid a purple-red, and acetic acid an aurora- 

 red. The last, by an excess of alkali, becomes again blue, 

 and if ammonia is the alkali employed, the solution is a 

 more delicate test for acids than litmus paper. In alkalies 

 which precipitate it from acids, even from water, it is inso- 

 luble. The dark-blue compound with lime, dissolves with 

 an aurora-red colour in acetic acid. An excess of ammonia 



burning of coal in the earth. 3. Artificial petroleum has so much resemblance to 

 oil of turpentine, that perhaps, we may infer petroleum to have been the oil of 

 turpentine of ancient times. 4. Eupion and petroleum are different principles. 

 Rectified coal tar oil contains, with other substances, petroleum and eupion. 

 />. The coal strata have not been exposed to higher temperatures. 6. Petroleum 

 wells appear to be the product of simple distillations of the coal strata through the 

 natural heat of the earth. 



