CHAPTER I. 

 PHOSPHORIC ACID. 



History. — The discovery of phosphorus is due to the alchemists. 

 In 1669, Brandt, a Hamburg merchant, searching for the philo- 

 sopher's stone in human urine, discovered an interesting substance 

 which he called yhosphorus, i.e. a body luminous in the dark. All 

 the phosphori known up to then — and there was quite a series of 

 them — to become luminous had to be previously exposed to sun- 

 light, and yet their luminosity soon vanished, whilst the new body 

 emitted a glow of its own accord, and preserved that property 

 permanently. It was, therefore, termed pJiosj^horus. Brandt kept 

 his process secret. But, in his turn, Kunkel, a Beilin chemist, 

 soon discovered phosphorus. In 1688, Albinus extracted phos- 

 phorus from mustard seed and cress seed. Thus within a few years 

 phosphorus was found in both the animal and vegetable kingdoms 

 without, however, anyone dreaming of its connexion with inorganic 

 nature. According to the cosmic theories of the times this sub- 

 stance was held to be the product of other bodies, or even the 

 result of spontaneous generation under the influence of ill -defined 

 vital forces. The scientists of the time had not yet distinguished 

 the chemical elements, the very simple theory of which was destined 

 in the future to furnish the very basis of the science of these bodies. 

 It is interesting, however, to observe that free phosphorus was 

 prepared and examined for seventy years without its compound 

 with oxygen, phosphoric acid, from which it had been isolated and 

 to which it so easily reverts, being known. Phosphoric acid was 

 not discovered till 1743, by Margraff, who ascertained its exact 

 nature and succeeded in re-converting it into phosphorus by calcining 

 it with charcoal. In 1769, Gahn, a Swedish chemist, found this 

 acid in bones, and a few years later Scheele, his countryman, 

 published a process by which phosphorus could be extracted from 

 bones, which is still used in its main features.^ Ten years after the 

 discovery of phosphoric acid in bones, and more than 100 years 

 after the first preparation of phosphorus, Gahn found this body 

 in the mineral kingdom also, viz. in lead phosphate (pyromorphite) ; 

 Vauquelin and Klaproth soon afterwards found, phosphoric acid in 

 apatite, that beautiful mineral, met with in large masses, the com- 



1 Scheele was by birth a Prussian. See Scheele's " Chemical Essays," Scott, 

 Greenwood and Son. 



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