228 HOW TO WORK 



according to these principles, we might often soon ascertain its true 

 nature. Of course there are many points requiring special attention, 

 Avhich, as already remarked, more strictly belong to chemistry than to 

 a work on the microscope ; and therefore I have confined myself 

 merely to an account of some of the leading principles involved in 

 this method of qualitative analysis. 



322. Substances giving well-marked Absorption Hands. The 

 following is a list of some objects, giving more or less well- 

 marked absorption bands, which can easily be prepared for examina- 

 tion : 



To be examined at once, not keeping well when diluted. 



Blood in water. 



Magenta, in water or alcohol. 



Mauve in alcohol. 



Aniline blue in alcohol. 



Brazil wood in water alone, and with bicarbonate of ammonia. 



Logwood ditto ditto. 



Blue Lobelia flowers in water. 



Keeping well for many months. 



Deoxidised ammoniacal haematin in water. 



Alkanet root in alcohol, with a little acetic acid. 



Alkanet root in alum, with a little alcohol. 



Colour of red Cineraria flowers in syrup. 



Cochineal in water. 



Cochineal in alum. 



Chlorophyll in alcohol. 



Chlorophyll in alcohol, with a little hydrochloric acid. 



Keeping well, probably for an indefinitely long time. 



Permanganate of potash in water, sealed up in a tube of glass 



which contains no lead. 

 Urano-uranic sulphate in water. 

 Chloride of cobalt in water. 

 Chloride of cobalt in a strong aqueous solution of chloride 



of calcium. 



Chloride of cobalt in absolute alcohol. 

 Crystals of binoxalate of chromium and potash. 



,, perchlorate of potash coloured with a little per- 



manganate of potash. 

 ,, native phosphate of uranium. 



,, acetate of uranium. 



,, chloride of cobalt. 



binoxalate or chromium and soda. 



