266 INJECTIONS. 



hours in running water, dried on parchment paper, and pre- 

 served as above. 



This injection mass is very well spoken of. 



Blue Gelatin Masses. 



474. Robin's Prussian Blue Gelatin Mass (see above, No. 462). 



475. Ranvier's Prussian Blue Gelatin Mass (Traite, p. 119). 

 Twenty-five parts of a concentrated aqueous solution of 

 soluble Prussian blue (prepared as directed below) mixed 

 with 1 part of solid gelatin. 



The mixture of the Prussian blue with the vehicle is effected 

 in the following manner : 



Weigh the gelatin, soak it in water for half an hour or an 

 hour, wash it, and melt it in a test-tube, in the water it has 

 absorbed, by heating over a water-bath. Put the solution 

 of Prussian blue into another test-tube, and heat it on the 

 same water-bath as the gelatin, so as to have the two at the 

 same temperature. Pour the gelatin gradually into the 

 Prussian blue solution, stirring continually with a glass rod. 

 Continue stirring until the disappearance of the curdy pre- 

 cipitate that forms at first. (Some gelatins produce a per- 

 sistent precipitate; these must be rejected; but it must be 

 borne in mind that the precipitate that invariably forms in 

 even the best gelatins disappears if the heating be continued. 

 It is essential to remember this when preparing Prussian blue 

 and gelatin mass.) As soon as the glass rod has ceased to 

 show blue granulations on its surface on being withdrawn 

 from the liquid, it may be concluded that the Prussian blue 

 is completely dissolved. Filter through new flannel, and 

 keep the filtrate at 40 over a water-bath until injected. 



The soluble Prussian blue for the above mass is prepared 

 as follows : 



476. Soluble Prussian Blue for Injection Masses (RANVIER, 

 ibid.). Make a concentrated solution of sulphate of peroxide 

 of iron in distilled water, and pour it gradually into a con- 

 centrated solution of yellow prussiate of potash. There is 

 produced a precipitate of insoluble Prussian blue. (An 

 excess of prussiate of potash ought to remain in the liquid ; 

 in order to ascertain whether this is the case take a small 



