30. For this kind of injection no colour is so commonly made use of as Prussian blue. It is not a good one, as was before stated, for any opaque object, as the light reflected from it appears almost black; yet by transmitted light no colour is more useful, because its distinctness is equally great by artificial light and ordinary daylight. The method of preparing this, as given by Dr. Beale, is as follows:--
Glycerine 1 ounce. Wood naphtha, or pyroacetic acid 1½ drachm. Spirits of wine 1 ounce. Ferrocyanide (yellow prussiate) of potash 12 grains. Tincture of sesquichloride of iron 1 drachm. Water 4 ounces.
Dissolve the ferrocyanide of potash in one ounce of the water; add the tincture of sesquichloride of iron to another ounce. Mix these solutions gradually together, shaking the bottle well which contains them--it is best to add the iron to the potash solution. When thoroughly mixed, these solutions should produce a dark-blue mixture, perfectly free from any perceptible masses or flocculi. Next mix the naphtha and spirits of wine, and add the glycerine and the remaining two ounces of water. This must now be slowly mixed with the blue liquid, shaking the whole well in a large bottle whilst the two come together. The tincture of sesquichloride of iron is recommended, because it can always be obtained of a uniform strength.
31. Dr. Turnbull used a mixture slightly different from the above, which is made with the sulphate of iron:--
Purified sulphate of iron 10 grains. Ferrocyanide of potassium 32 grains. Glycerine 1 ounce. Pyroacetic acid 1½ drachm. Alcohol 1 ounce. Water 4 ounces.
Dissolve the sulphate of iron in one ounce of the water, gradually add the ferrocyanide of potassium dissolved in another ounce, and proceed as above.
32. Dr. Beale also gives us the following carmine injection to be employed in the same way as the blue.[G] Take--
Carmine 5 grains. Glycerine, with 8 or 10 drops of hydrochloric acid ½ ounce. Glycerine (pure) 1 ounce. Alcohol 2 drachms. Water 6 drachms.
Mix the carmine with a few drops of water, and when well incorporated add about five drops of liquor ammoniæ. To this dark-red solution about half an ounce of the glycerine is to be added, and the whole well shaken in a bottle. Next, very gradually pour in the acid glycerine, frequently shaking the bottle during admixture. Test the mixture with blue litmus-paper, and if not of a very decidedly acid reaction, a few more drops of acid may be added to the remainder of the glycerine and mixed as before. Lastly, mix the alcohol and water very gradually, shaking the bottle thoroughly after adding each successive portion till the whole is mixed. This fluid may be kept ready prepared, and injections made very rapidly with it.