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- 



<5> O 



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- 







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). 



