REPORT ON SWEET SPIRIT OF NITRE 
155 
object-glasses in micro-photography rather than the highly corrected ones of first-class 
makers. Mr. Brady and Mr. Sutton, on the other hand, contended that the best results 
were obtained by the use of first-class objectives, correcting the focal distance according 
to experience for the difference between the visual and chemical foci. 
REPORT ON SWEET SPIRIT OF NITRE. 
BY W. LAIRD, PH. C., DUNDEE. 
Twenty-one samples were sent from Dr. Attfield, apparently all procured 
from shops in Englaud, some old and others recent. Following the course I 
adopted on a former occasion, I first comment on their external appearances, 
the most noticeable of which was the different effects shown by tiie mode of 
dispensing this article. Four of them were put up in stoppered bottles, and 
were full, bright, and clear as when they left the bauds of the dispenser, while 
all the rest were more or less discoloured from the decomposition of the corks, 
which, in some instances, were almost as much consumed as if they had been 
in vials of dilute nitric acid. Some of them had leaked or evaporated so much 
as to be more than half empty, so little being left that they could not float the 
hydrometer. 
No. 7, 10, and 19 were the only samples having presentable corks in them, 
owing apparently to the sweet spirit of nitre therein being less acid than that 
in the others, though they had evidently been dispensed with equal care. The 
natural deduction from this is, that in every case where spirit of sweet nitre is 
likely to be kept for any length of time, whether in family or ship’s medicine 
chests, it ought to be put up in stoppered bottles. I forward some of the corks 
to show their state. All the samples were acid, No. 7 and 10 least, and No. 9 
most, as will be seen on reference to the accompanying vials I have sent, as 
being better than any written description of the degrees of acidity. Each of 
them contains one grain of iodide of potassium and fifteen minims of sweet 
spirit of nitre w T ith water, showing the free acid by liberation of iodine. No. 
10 is now almost colourless, the small portion of iodine having been absorbed 
by the cork. No. 9 shows the effect of neutralizing the acid with Mag. Carb., 
and is shown with a hope of eliciting an answer to the question, u Should sweet 
spirit of nitre be neutralized before being sold, or should we sell it just as it 
chances to be P” 
The sp. g. of No. 5, H. and S. was *830, No. 12, B. and S. *837, and No. 16, 
T. C. P. ’838, showing them to have been made according to the Ph.L. instead 
of the Ph.B. No. 7, G. Y. S. -842, No. 9, A. and H. -840, No. 15, W. R. and 
C. S. ’848, No. 18, *845, and No. y 8 , ‘840, are as nearly equal to the Ph.B. 
strength as could be desired. Nos. 8, J. P., 10, W. M., 13, R. C. P., 14, G., 
and 19, T. S. G., were all *850, which, according to this and previous reports, 
seems to be the strength most commonly sold. No. 2, F. M. R. is marked as 
having been originally '843, but is now only '860, having, I presume, suffered 
this diminution of strength by evaporation round the wasted cork,—a dilution 
equal to its having rather more than 10 per cent, of water added. No. 4, W. 
Y. is '930, and No. 11, T. P. is '928, the bottles being quite full, the corks in 
good condition, and No. 11 tied over and sealed just as it left the sellers’ hands. 
I have, therefore, no choice left but to say of them that if originally good, they 
have been adulterated with equal parts of water. 
So far this inquiry has been satisfactory, having shown a much better result 
than my previous one,—a tenth part only being chargeable with wilful adultera¬ 
tion , whereas in my former one there were rather more than a third. Let us 
