136 
BRITISH PHARMACEUTICAL CONFERENCE. 
The constancy of the spectra is very great if only ordinary care and a good 
spectroscope be used. When a microscopist has once found out the most com¬ 
fortable and advantageous position of his instrument and illuminating appa¬ 
ratus, he had better always use the same. I always prefer a paraffin lamp 
mounted on a sliding stand, which I place to the right of my microscope, and 
have the red end of the spectrum to the left, simply because, from force of habit, 
it seems to suit my spectroscope better, and by so placing them I can at any 
time set to work in a few minutes. . 
Some of the spectra of medicinal preparations, as Tinct. Hyoscyarai, Tinct. 
Cannab. Ind.. Tinct. Lobelise iEtherea, are extremely beautiful, and will vie 
with any of the mineral salts commonly employed as show objects. _ 
Microspectroscopic observations promise well to detect adulteration and sub¬ 
stitution, for hardly ever do the spectra of any two articles appear exactly the 
same. The smallest discrepancy is immediately seen when the spectra are placed 
side by side by means of the additional prism. 
It cannot be doubted that the use of the microspectroscope is of the greatest 
assistance in many analytical researches. It must not be expected that every 
mixture will show separately the several constituents by their individual peculia¬ 
rities. This is only true in a few instances *, cochineal may be at once detected in 
Tinct. Cardam. Co. and Tinct. Cincbon. Co. . 
The colouring matter of blood will show its own bands when mixed with 
cochineal. The spectrum of a tincture made with the leaves of the biennial 
henbane differs entirely from that of the annual. 
It is often the task of the geologist to say whether a clay contains the prot¬ 
oxide or peroxide of iron or both. Spectral analysis will determine the ques¬ 
tion at once, and point out the protoxide, peroxide, or magnetic oxide. 
Another instance is when factitious syrup of violets is sold. The spectroscope 
will at once tell whether the colouring matter is litmus or red poppy. 
Time will not allow me to give more instances of the utility of spectral ana¬ 
lysis, but as I before stated, it is a very extensive field for future observation, 
and a source of great interest and pleasure for many an hour of recreation and 
instruction. 
The following are spectra of many of the Pharmacopoeial preparations most 
generally used. 
Inf. Rosae Co. —Green extended over yellow, blue and violet quite absorbed. 
When alum is added, the green is totally absorbed, forming a very dark, broad 
band; part of the blue and all the violet are also absorbed. 
Inf. Calumbse. —Violet and half the blue absorbed. 
Inf. Rhei. —Violet, blue, and part of the green absorbed. # 
Tinct. Aloes Barb. (Simp.).— Only the red portion of the spectrum transmitted, 
all the remainder absorbed. 
Tinct. Aloes Socot. (Simp.). —Green, blue and violet absorbed. 
Tinct Aloes Capens. (Simp.). —Green, blue and violet absorbed. 
Tinct. Arnicse.— All the violet and a small part only of the blue absorbed. 
Tinct. Aurantii. —The green extended over the yellow, while half the blue and 
all the violet are absorbed. 
Tinct. Caiumbse. —Violet, blue and two-thirds of the green absorbed. 
Tinct. Cannab. Indie.—A beautiful spectrum showing the dark chlorophyll 
band strongly at line B. The green extended over yellow, and all the blue and 
violet absorbed. 
Tinct. Cardam. Co.—Violet and blue absorbed. When diluted, the strong 
cochineal line is visible at E. 
Tinct. Cascarillce. —Violet, blue and one-third of green absorbed. 
Tinct. Curcumse. —Blue and violet absorbed. 
Tinct. Cbiraytce. —As Tinct. Cascarillae. 
