( 278 ) 
XII. — On Purifying the Air of Stables by a mixture of Gypsum 
or Sawdust loith Sulphuric Acid. By Henry Reece. 
Having been invited by Mr. Evans, of Dean House, Enstone, to make 
some experiments on his excellently-conducted farm and stables, I 
trust the results of those upon the absorption of ammonia may prove of 
sufficient interest to entitle them to publication. As gypsum (crystal- 
lized sulphate of lime) had been highly recommended for this purpose 
in some recent works on agriculture, the stables were in the first in- 
stance freely strewn with this salt coarsely powdered ; but though the 
ammonia was evolved during the removal of the wetted straw in sufficient 
quantity to affect even the eyes of the grooms, I could not, after two 
days' exposure, detect the slightest trace of it in the gypsum when 
I examined it with slaked lime. This result was the more surprising, 
as it is known to every chemist that solutions of carbonate of ammonia 
and of gypsum are incompatible; the carbonic acid leaving the ammonia 
to form the precipitate carbonate of lime, the sulphuric acid passing to 
the ammonia ; and I had previously ascertained that in an atmosphere so 
highly charged with ammonia as to be destructive to animal or vegetable 
life, a very appreciable pro])ortion was taken up by wetted gypsum. 
The following experiments appeared conclusive upon the point, that 
imder less favourable circumstances not an atom was absorbed : 200 
grains wetted with distilled- water were exposed in a close stable for 
three days, precautions having been taken to avoid any error from eva- 
poration : it was again weighed, no increase could be perceived, nor was 
any ammonia evolved on the application of the usual tests ; while 200 
grains wetted with diluted sulphuric acid, and exposed the same time, 
were found to have gained 36 grains of ammonia. The stables were then 
strewn with the gypsum moistened with sulphuric acid, and examined 
the next morning : every portion was found to have absorbed sufficient 
ammonia to evolve its peculiar pungent odour when brought in contact 
with slaked lime ; the stables had also lost their close, unhealthy smell. 
To use the words of the grooms, they ap])eared sweetened. As it was 
evident the gypsum acted merely mechanically, affording a convenient 
absorbent surface for the acid, experiments were made, substituting saw- 
dust for gypsum with even more favourable results. That tiie propor- 
tion of free ammonia in stables is very large maybe shown by the simple 
experiment of placing a moistened piece of litmus-paper reddened with 
weak acid in a stable : in one badly cleaned or ill-ventilated the effect 
is instantaneous ; but even in those of Mr. Evans, where the greatest 
attention was paid to these points, the paper was observed in a few 
minutes to become blue ; even the water kept in the stable the over- 
night, as is the habit to take off the chill, becomes sufficiently impreg- 
nated with ammonia to affect tests. As this alkali is justly ranked 
among the most powerful stimulants, the continual breathing of an at- 
mosphere vitiated by it can hardly fail to have a prejudicial effect. 
Grooms are observed to be short-lived ; and the rapid course of inflam- 
matory diseases in horses, and their distressing predisposition to colds and 
affections of the chest, are no doubt greatly aggravated by this cause. 
