Erdmann on Indigo : Wcehler on Formic Mther. 209 



C'«H*NCl-0'. Treated with potash it forms a bichlori- 

 satinic acid, which may be precipitated from its solution in 

 potash by means of an acid, in form of a yellow powder ; 

 this acid is tolerably soluble in water ; it is easily decomposed ; 

 its aqueous solution decomposes at 60°, or even in the cold ; 

 it contains one atom water of crystallization. {Journal fiir 

 Praktische Chemie. Erdmann and Marchand, xix. 321). 



The potash salt crystallizes in needles and leaves. For- 

 mula C"5 H^ N CI- O^ . K ; the crystallized salt contains two 

 atoms of water. The baryta salt crystallizes in the same form, 

 and contains two atoms of water. The copper salt is at first of 

 the colour of hydrated oxide of iron, but becomes carmine red 

 and granular; when pressed assumes a golden lustre. The 

 silver salt is partly soluble in water, and may be crystallized ; 

 it is anhydrous. 



The more of the resinous substance is formed the more 

 chloride of indopten is produced ; it is not formed by the 

 action of chlorine on the proto- or bichloride of isatin. 

 The resin examined was not quite pure, for the product 

 formed by the action of chlorine on indigo-red was always 

 mixed with it; it is obtained in small quantities. The for- 

 mula appears to be C^° H« Cl^ N^ O', or C^«H'« CI* N 0'°. 



It is probable that the ammonia resin, and chloride of 

 indopten are unimportant and variable products. 



By the action of bromine similar substances are produced, 

 bromide of indopten ; and by potassa, bromindatmit and bro- 

 mindoptenic acid. They have apparently the same formula as 

 tlie chlorine compounds ; also bromide of isatin and bromi- 

 satinic acid, bibromide of isatin and bibi'omisatinic acid : they 

 have the same composition, and are in other respects very 

 similar to the chlorine compounds. 



In a second paper Professor Erdmann promises to make 

 known the action of certain reagents on the bodies described 

 above. 



Formic aether may be prepared, according to Wcehler, by 

 distilling a mixture of ten parts of starch, thirty-seven parts 

 finely powdered binoxide of manganese, thirty parts ol" sul- 

 phuric acid, fifteen parts of water, and fifteen of mere al- 

 cohol. In the product of the distillation chloride of calcium 

 is dissolved, and the aether distilled off in a water bath ; 

 from the solution of chloride of calcium in the aether, small 

 yellow crystals are sometimes deposited : they have not been 

 further examined. {Annalen der Chemie und Pharmacie^ xxxv. 

 238.) 



Phil. Mag. S. 3. Vol. 18. No. 116. March 184-1. P 



