PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 53-9 



the artificial blue coloring matter obtained by acting on chinoline 

 with iodide of amyl, and known as " cjanin." This body is so 

 readily acted upon by acids and bases, and its tinctorial power is 

 so enormous, that its delicacy as a test for either acids or bases is 

 quite marvellous. It Avill detect the presence in water of one- 

 millionth of either sulphuric acid or caustic potash, and of quanti- 

 ties of carbonic acid which cannot be detected by means either of 

 limes or of barytes. Pure distilled water colored with it so as to 

 be quite blue while preserved from contact with the atmosphere, 

 has its color instantly destroyed l)y being blown into from the 

 lungs, by reason of the carbonic acid in the expired breath. 

 Magnesia is incapable of dissolving in water to a sufficient extent 

 to enable the solution to react upon litmus, but pure water in 

 which magnesia has been shaken up gives a most distinct alkaline 

 re-action with cyanin. So does distilled water which has had oxyd 

 of lead shaken up in it, albeit sulphureted hydrogen, which will 

 detect one part of lead in 350,000 of water, is incapable of show- 

 ing that any oxyd of lead has been dissolved. 



Kreosote and Carbolic Acid. 

 Prof. A. Y\ Hoffman, now at Berlin, has shown quite recently 

 that these two substances, the one obtained from vegetable, the 

 other from mineral tar, are essentially identical, and do not, as has 

 hitherto been very generally assumed, possess different re-actions. 

 Still the kreosote of wood used in medicine must not be replaced 

 by carbolic acid, since it is now proved to contain some admix 

 tures which the latter acid does not have. 



Transformatiox of Nitrate of Soda into Nitrate of Potash, 

 M. Condurie has patented the following processes. He makes 

 concentrated and equivalent solutions of nitrate of soda and chlo- 

 ride or sulphide of barium, and mixes the solutions. Nitrate of 

 baryta, which is but sparingly soluble, is precipitated. It is well 

 washed and then l)oiled with sulphate of lead, whereby nitrate of 

 lead and sulphate of baryta are produced. The nitrate of lead is 

 now boiled with sulphate of potash, and so nitrate of potash is 

 formed and sulphate of lead reproduced. 



Process for the Condensation of Ammoniacal Gas. 

 Knab has found that chloride of calcium absorbs its own weio-ht 

 of ammoniacal gas, Avhich is again evolved on the application of 

 heat. The chloride will serve an indefinite time. M. Knab coi> 



