ABSORPTION OF ASH-CONSTITUENTS 



91 



phuric acid is added, which forms needle-like crystals of calcium sulphate (gyp- 

 sum) in the presence of this element (Fig. 53). Magnesium crystallizes, 

 as ammonium-magnesium phosphate (in a great variety of forms), upon the 



Fig. 52.— Crystals of potassium chloroplatinate. Fig. 53.— Crystals of calcium sulphate. 



addition of sodium phosphate and ammonia (Fig. 54) . Iron is identified by the 

 blue color produced with potassium ferrocyanide. Phosphates are identified 

 by treatment with a solution of ammonium molybdate in nitric acid, greenish- 





Fig. 54. — Crystals of ammonium magnesium 

 phosphate. 



Fig. 55. — Crystals of ammonium phospho- 

 molybdate. 



yellow crystals of ammonium phospho-molybdate being formed and gradually 

 becoming bright green (Fig. 55). Upon addition of strontium nitrate, sulphur 

 separates out as small rounded crystals of strontium sulphate (Fig. 56). An- 



^0 0°^ 



Fig. 56— Crystals of strontium sulphate. Fig. 57.— Crystals of thallium chloride. 



other test for sulphuric acid is the addition of caesium chloride and aluminium 

 chloride, which leads to the formation of large crystals of caesium-alum. Chlor- 

 ides may be identified by adding thallium sulphate, with the formation of 

 characteristic crystals of thallium chloride (Fig. 57). 



