PHOSPHORUS. 1 99 



trading chemists, and kept for sale in apothe- 

 caries' shops. 



It crystallizes in rhomboids, has a cooling and 

 somewhat bitter taste, and effloresces when kept 

 in a dry atmosphere. I have met with this salt 

 consisting of 11 atoms, and likewise of 12 atoms 

 of water combined with one integrant particle 

 of anhydrous phosphate of soda. By far the 

 most common proportion of water, however, is 

 12 atoms. This difference in constitution, as 

 far as the aqueous part is concerned, probably 

 depends upon the way in which it has been kept. 

 It very speedily effloresces when exposed to the 

 air. Now, when got from the shops, we often 

 perceive white effloresced spots scattered through 

 the crystals. It is in such cases that the water 

 of crystallization is sometimes reduced to 11 

 atoms. We can never depend upon the water 

 of crystallization, unless the salt be quite trans- 

 parent. I think it best to make it anhydrous 

 by heating it red hot, and keeping it for some 

 time in a state of fusion in a platinum crucible. 



7*5 grains of anhydrous phosphate of soda, 

 and 2O75 grains of crystallized nitrate of lead, 

 were dissolved in separate portions of distilled 

 water, care being taken not to employ more 

 water than was sufficient to dissolve the salts 

 completely. These two solutions being mixed 

 together, a double decomposition took place ; 

 phosphate of lead precipitated in the slate of a 



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