248 Mr Silliman on the 



bonate of lime ; the solution should have been recently 

 boiled, and the test applied while it is yet hot, the air being 

 excluded ; and the precipitate should be immediately col- 

 lected on a filter and washed. If the precipitate by lime- 

 water be fused in a platinum capsule, with carbonate of soda, 

 or carbonate of potassa in excess, the phosphoric acid is all 

 transferred to an equivalent portion of alkaline base, while 

 the lime or magnesia, or the base with which it was before 

 united, will remain as a carbonate. The usual tests, which 

 have already been enumerated, will shew the presence of the 

 phosporic acid. 



The lime-water test offers far the best means of separating 

 from the lime (which exists as a carbonate) all the other 

 constituents of a coral, as these various substances are in a 

 very small quantity compared with the entire mass of the 

 coral. Some easy means of completely separating them all, 

 is an indispensable preliminary step in their examination 

 and estimation. 



I am indebted to my friend Dr J. L. Smith, of Charleston, 

 South Carolina, for suggesting to me the use of this test in 

 the analysis of the corals. 



As the several elements whose presence our researches 

 have determined in corals, have been enumerated in the 

 body of the work (p. 57), it is not necessary to repeat them 

 here ; but we may state, in a summary manner, an outline 

 of the general course of analysis pursued in determining the 

 constitution of the lime-water precipitate, which, it will be 

 allowed, contains several elements whose association has al- 

 ways been considered as offering some of the most difficult 

 problems in the whole range of inorganic analyses. The 

 following plan of analysis has been contrived in part from 

 the late researches of Rammelsberg, on the estimation of 

 phosphoric acid, and partly from the labours of Rose and 

 Berzelius, adapting the method to the requirements of the 

 particular problem before us. 



A. The lime-water precipitate, after ignition, is weighed 

 and then digested in fine powder in cold chlorohydric acid ; 

 it slowly dissolves, leaving a white flocculent powder. This 

 collected and washed, will be found to be silica. It is harsh 



