92 Ilhtorkal Sketch of Improvements in [Aug. 



four parts of old linen rags were reduced into a mucilage with 

 34 parts of strong sulphuric acid. The acid solution being 

 diluted with water, 3-6 parts of undecomposed hgnin fell. The 

 acid liquid thus diluted was boiled for 10 hours, and then satu- 

 rated with carbonate of lime. The filtered liquid being evapo- 

 rated to dryness, left a sweet-tasted matter, which weighed 23*3 

 parts. This matter gradually crystallized, and exhibited all the 

 characters of sugar of starch. 



The vegeto-sulphuric acid was separated from the sugar by 

 means of alcohol ; but the alcohol dissolved not merely the acid, 

 but likewise a portion of the sugar. The solution being evapo- 

 rated to dryness was treated with sulphuric ether, which dis- 

 solved the acid, but left the sugar. This acid is deliquescent, 

 and cannot be crystaUized ; it is nearly colourless, has an 

 exceedingly sour taste, and sets the teeth on edge. When 

 heated, it becomes black, and if it be diluted with water, black 

 flocks of charcoal separate. When heated above the tempera- 

 ture of boiling water, it is decomposed, and sulphurous acid 

 exhales. It does not precipitate a single metallic solution, and 

 all the salts which it forms are soluble in water. None of its 

 salts seems capable of crystallizing. The nature of this acid has 

 not hitherto been determined. It possesses some characters 

 similar to those of hyposulphuric acid, but some of its other 

 properties differ entirely from that acid. 



When equal weights of caustic potash and sawings of wood 

 are heated in a silver or iron crucible, stirring the mixture con- 

 stantly at a certain temperature, it softens and dissolves 

 completely, swelling up greatly at the same time. If it be now 

 taken from the fire, and water pouied upon it, the whole dis- 

 solves with the greatest facility, and we obtain a dark-brown 

 liquid, consisting of a combination of potash and idmin dissolved 

 in water. If anacidbedropped into this liquid, the ulrain falls down 

 in great abundance, and requires only to be washed and dried. 



Artificial ulmin thus obtained has a brilliant black colour, hke 

 jet. It is very brittle, and easily broken into angular fragments. 

 It has no smell, and little taste. In this state it is insoluble in 

 water; but when just precipitated, and still moist, water 

 dissolves •j-j^'o-o of its weight of it. The solution is coffee- 

 coloured. Nitrate of silver, persulphate of iron, nitrate of 

 barytes, acetate of alumina, muriate of lime, muriate of soda, 

 throw down brown precipitates from it, but they do not appear 

 till some time after the reagents have been added. Lime and 

 litharge deprive the water entirely of its colour. It is soluble in 

 concentrated sulphuric acid, and precipitated by water. Alcohol 

 dissolves it with facility, and forms a dark-brown liquid which is 

 precipitated by water. (Ann. de Chim. et de Phys. xii. 172.) 



XIII. Animal Substances. 

 1. Picromel. — This substance though it constitutes the charac- 



