446 NOTES ON PRESCRIBING. 



1867. The writer of this formula was a frequent prescriber of 



BariunTchlo- chloride of barium which he generally ordered in combination 

 ride rendered w jth sulphate of quinine or sulphate of iron, or with both, 

 thereby probably rendering the chloride inert. No reliance 

 could of course be placed on the uniform effects of baryta, pre- 

 scribed sometimes in a state of activity and sometimes in an inert 

 form. 



As another example of this character, take the following pre- 

 scription which was brought to be dispensed a few weeks ago : 



R Potassii iodidi 9i 



Potassse bicarbonatis 3iss 

 Ferri et quinae citratis iv 

 Tinct. valerians ammoniatse j 

 Aquae ad iv 

 Misce. Suinat cochleare medium ex aqua ter die. 



Fault in In preparing this medicine, the iodide and bicarbonate were dis- 

 prescnbmg. so } vec [ j n a portion of the water, to which the tincture was then 

 added. The citrate was dissolved in the remainer of the water 

 and the two solutions were mixed. The result, as might be ex- 

 pected, was that a frothy white precipitate of quina was in- 

 stantly formed which in a few minutes collected into a coherent 

 mass, sufficiently hard and tough to be rolled into pills. 



It may be observed that in compounds such as this, the quina 

 is not subject to the remarkable influence which citric or tartaric 

 acid exerts on peroxide of iron, that of allowing it to be combined 

 with an alkaline bicarbonate or with ammonia, but that it is 

 more or less separated when such alkalies are mixed with it, a 

 fact very often overlooked. 



Unsuitable A third instance of extremely unsuitable combination occurs 

 combination. ^ Q me ^ W ] 1 i c i 1 from its frequency a few years ago was impressed 

 on my memory, although I have no copy of a prescription in 

 which it was ordered. It was the prescribing of glacial phos- 

 phoric acid in pills, and that in combination with valerianate of 

 zinc! 



FORMULAE THAT GIVE HISE TO UNEXPECTED COMBINATIONS. 

 A very interesting fact bearing on this point has been stated in 





