Dr. Schuuck on the Formation of Indigo-blue. 125 



meaug of carbonate of lead, and the liquid having been filtered, 

 sulphuretted hydrogen was passed through it in order to preci- 

 pitate a little lead contained in it, and after being again filtered, 

 it was evaporated by means of a current of air in the sanie appa- 

 ratus as that employed in the evaporation of solutions of indican. 

 After the evaporation was completed, there was left a light brown 

 syrup, which on being treated with alcohol was usually entirely 

 dissolved. The alcoholic solution was filtered if necessary, and 

 then mixed with about twice its volume of ^ther, which imme- 

 diately turned it milky and produced a deposit consisting of a 

 brown syrup. This syrup was allowed to settle, and the whole 

 was left to stand for twenty-four hours. The surface of the 

 syrup and the sides of the glass vessel were then found to be 

 covered with a quantity of small, almost white crystals. These 

 crystals are the same as those referred to above as being obtained 

 in the preparation of indican, when sether is added to the alco- 

 holic solution of the latter. I was at first inclined to suppose 

 that they consisted of a substance which was contained as such 

 in the plant, but I soon discovered that they were a product 

 of decomposition of indican, as they were also obtained from per- 

 fectly pure indican, which had been prepared by successive solu- 

 tion in alcohol, water and aether, in the last of which the crystals 

 are insoluble. Indeed no product of decomposition of indican 

 seems to be so easily formed as this. By shaking the liquid from 

 which they were deposited, the crystals were easily detached from 

 the sides of the vessel and the surface of the syrup. They were 

 collected on a filter, washed with sether, and then pressed between 

 folds of blotting-paper, in order to absorb any of the syrup which 

 might be mixed with them. They were then dissolved in boil- 

 ing water, and the solution having been decolorized with animal 

 charcoal, was filtered and evaporated, when it left a crystalline 

 mass, which was again pressed between blotting-paper, and dis- 

 solved in a small quantity of boiling alcohol. The alcoholic 

 solution on cooling deposited a mass of small crystals, which had 

 the properties and composition of 



Leucine. 



It crystallized from the alcoholic solution in small flat tables 

 having a pearly lustre, which repelled cold water like a fatty 

 acid, but were readily soluble in boiling water. It was insoluble 

 in aithcr. "When heated in a tube, it was completely volatilized 

 without melting, forming a sublimate on the colder parts of the 

 tube in the form of a light mass like cotton. It was easily 

 soluble, even in the cold, in sulphuric, muriatic and nitric acids. 

 The solution in nitric acid gave ofi" no nitrous fumes on being 

 boiled, and left on evaporation a colourless syrup, which on 



