Ammonia. 277 



way as potash. It is to be remarked, that 49 gran (46-9 grs.) 

 of sulphuric acid require 143 gran (137-1 grs.)* 



The chemical blue calico may be used for the same object ; 

 hence, a known quantity of pure carbonate of soda gives 

 a standard to judge of the other kinds. For this purpose 

 a solution of 2 grans (1-918 grs.) of pure crystallized car- 

 bonate of soda are heated with 300 grans (287-7 grs.) of 

 water and as many pieces of cotton are to be added as shall 

 be decolourized. In other respects the proceeding may be 

 conducted as with potash. 



Ammonia. — Occurs in commerce under the name of spirit 

 of salmiac, forming a clear solution with a pungent odour. 

 When solution of ammonia is placed in an open vessel in 

 the air or heated, the ammonia is dissipated and pure water 

 remains. Ammonia, therefore, although it has almost all 

 the properties of potash and soda, should not be employed 

 when it can be volatilized. 



Hence, ammonia does not answer for printing alone. As 

 it dissolves many substances, for example, oxide of copper; 

 it is employed to bring it upon calico, in which case the 

 ammonia is volatilized and the copper colour remains upon 

 the calico. 



If we blow tobacco smoke upon paper coloured with 

 Berlin blue it acquires a reddish colour. This proceeds 

 from the ammonia which is contained in tobacco smoke. 

 Here then ammonia itself produces the change of colour. 

 Chemical blue calico also acquires a violet colour from 

 ammonia. In stables where much ammonia is disengaged 

 the same action is always produced. 



A calico manufacturer once sent some chemical blue 

 goods packed up in a box, the empty portion of which was 

 filled up with straw. The whole of the goods in the vicinity 

 of the straw were found when unpacked to have become as 

 blue as a violet. It turned out that the straw had been 

 taken from a stable where it had been in contact with urine 

 and other substances containing ammonia. 



In printing rooms where mordants containing ammonia, 

 for example, ammoniuret of copper, are printed, no chemi- 

 cal blue goods should be allowed to hang. 



* The atomic numbers are 50 parts sulphuric acid of sp. gr. 1-847 to 146-9 

 carbonate of soda.— Edit. 



