A manual of chemistry : theoretical and practical, inorganic and organic, adapted to the requirements of students of medicine / by Arthur P. Luff and Hugh C.H. Candy.

  • Arthur P. Luff
Date:
1910
Catalogue details

Licence: In copyright

Credit: A manual of chemistry : theoretical and practical, inorganic and organic, adapted to the requirements of students of medicine / by Arthur P. Luff and Hugh C.H. Candy. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    83/644 (page 67)
    chap, iv] FORMULAE OF SALTS G7 HoS04, just as the formulae of oxides were obtained from H20 ; S04 now occurs in place of 0. The student should find no difficulty in constructing the formula of any salt of a monobasic or dibasic acid. He will, however, sometimes require the formulae of salts of a tribasic acid such as H3P04, and as this seems often to present more difficulty to beginners (for whom this book is more especially written), it will now be explained. The orthophosphates of a monad metal such as sodium Na* will evidently be represented by the three formulae : NaiH2P04 Na'aHPO* Na'3P04 All exist, but the second is the common sodium phosphate employed in medicine; an aqueous solution of it is one of the laboratory reagents. Three orthophosphates of a dyad metal, such as calcium, are also possible, but their formulae are not quite so easily obtained, because in this case the dyad atom can only replace the typical H atoms, two at a time. From H3P04 we can therefore only obtain CaHP04 ; to obtain the other salts we must double H3P04, and from the H6(P04)2 so obtained we easily derive Ca''3(P04)2, the normal phosphate used in medicine and the chief mineral constituent of our bones ; and also CaH4(P04)2, a much more soluble salt. The normal phosphate of a triad metal like iron is easily formed from H3P04, since a triad atom can replace the H atoms three at a time. Iron will therefore form two normal phosphates : Ferrous phosphate Fe3(P04)2 and Feme phosphate FeiiiP04. Both are present in the iron phosphate used in medicine. It may be convenient to mention here that the