VIII. ACIDS.— Prussic. 301 



Scheele's acid of Pkussian blue, Acide hi/dro-ci/anique, 

 Acidum Prussiamu Prussian blue 2oz., calcined mercury 6oz., 

 distilled water 6oz. : boil till the blue colour is changed to a 

 yellowish green, fiher, add hot water 10 oz., to wash the sediment 

 perfectly, pour the liquor upon clean iron filings 3iij, and add oil 

 of vitriol 3J ; pour the liquid from the quicksilver that has sepa- 

 rated, and distil till l-4th part has passed. 



La Planche^s Prussic acid. Proceed as before, but draw off 

 only l-6th, and redistil upon chalk, gr. ij to the oz., drawing off 

 only 3-4ths. 



Gay Lussacs Prussic acid. To prussiate of quicksilver 3 oz., 

 contained in a tubulated retort connected with two receivers sur- 

 rounded with ice and salt, the first of which contains pieces of 

 muriate of lime and chalk ; add slightly-smoking spirit of salt ^ oz. ; 

 distil with a slight heat, until some water appears in the first 

 receiver, then stop the distillation, and take away the freezing 

 mixture of ice and salt from the first receiver only : the Prussic 

 acid will distil over into the second smaller receiver, leaving the 

 water with the dry muriate of lime, and the muriatic acid with 

 the chalk. 



Magendies medicinal Prussic acid. Gay Lussac's Prussic acid 

 3j, distilled water 5viijss, by weight; or acid 3j, distilled water 

 3vj, by measure ; antispasmodic. 



Scheeles Prussic acid as prepared by the Paris apothecaries. 

 Gay Lussac's acid 3j, water 5x1. 



ScheeWs Prussic acid as prepared by liohiquet. Gay Lussac''s 

 acid 3j, water 3ij. 



Scheele's Prussic arid as ordered in the Paris Codex Medic, 

 Gay Lussac's acid 5j, water 5j. — Strong Prussic acid in very 

 small quantity, gtt. j — ij, either applied to the tongue or even to 

 the skin, kills instantaneously, and the body exhales for several 

 days a strong smell of bitter almonds ; gtt. vj — x of Scheele's or 

 La Planche's acid in water 3iij to iv, taken by tea-spoonsful every 

 two hours is beneficial in chronic cough and in phthisis. 



Serious, and sometimes fatal, accidents have been occasioned 

 by the want of uniformity in the strength of Prussic acid. For 

 the purpose of obtaining such uniformity, Mr. Everitt, Professor 

 of Chemistry to the Medico- Botanical Society, has proposed the 

 following process: — " Into a phial capable of holding rather more 

 than one fluid ounce, put M) grs. of the cyanurct of silver, add 

 7oz. 10 minims of water and 10 minims of the dilute of hydro- 

 chlorate acid, cork closely, shake several times for the first (juar- 

 ter of an hour, set aside to allow the chloride of silver to fall, 

 decant the clear liquid into another bottle, to be preserved for 

 use ; every fluid drachm will contain one grain of real hydrocy- 



