EPITHELIAL AND CONNECTIVE TISSUES 337 



EXPERIMENT ON OSSEOUS TISSUE 



The percentage composition of normal human bone and of bone from 

 a case of osteomalacia is given in the following table: 1 



Qualitative Analysis of Bone Ash. Take i gram of bone ash in a small 

 beaker and add a little dilute nitric acid. What does the effervescence indicate? 

 Stir thoroughly and when the major portion of the ash is dissolved add an equal 

 volume of water and filter. To the acid filtrate add ammonium hydroxide to 

 alkaline reaction. A heavy white precipitate of phosphates results. (What 

 phosphates are precipitated here by the ammonia?) Filter and test the filtrate 

 for chlorides, sulphates, phosphates, and calcium. Add dilute acetic acid to 

 the precipitate on the paper and test a little of this filtrate for calcium and phos- 

 phates. Heat the remainder of the filtrate to boiling and add (NH^aCOs and 

 NH 4 C1 slowly to this hot solution as long as a precipitate forms. Filter off the 

 precipitate of CaCO 3 and wash with hot water until free from alkali. 2 Add a 

 solution of NajjHPO^ make strongly alkaline with NH 4 OH, and note the forma- 

 tion of a white precipitate of ammonium magnesium phosphate (NH^MgPO^ 

 Examine the crystals under the microscope and compare with those shown in 

 Fig. 129, page 408. To the precipitate on the filter paper, which was insoluble 

 in acetic acid add a little dilute hydrochloric acid and test this last filtrate for 

 phosphates and iron. 



Reference to the following scheme may facilitate the analysis. 



1 McCrudden: Jour. Biol. Chem., 7, 199, 1910. 



2 Magnesium is not precipitated here because of presence of NHC1. 



22 



