§§ I27-I3 1 *] SODIUM, POTASSIUM, AND AMMONIUM SALTS. I 33 
of the pulse. The rise in the blood-pressure occurs even after section of the spinal 
cord. Somewhat larger doses cause rapid lowering of the blood-pressure, and apparent 
cessation of the heart’s action ; but if the thorax be then opened, the heart is seen 
to be contracting regularly, making some 120-160 rhythmic movements in the 
minute. If the respiration be now artificially maintained, and suitable pressure 
made on the walls of the chest, so as to empty the heart of blood, the blood-pressure 
quickly rises, and natural respiration may follow. An animal which lay thirty-six 
minutes apparently dead was in this way brought to life again ( Bohm ). The action 
of the salts of potassium on the blood is the same as that of sodium salts. The blood 
is coloured a brighter red, and the form of the corpuscles changed ; they become 
shrivelled through loss of water. Voluntary muscle loses quickly its contractility 
when a solution of potash is injected into its vessels. Nerves also, when treated 
with a 1 per cent, solution of potassic chloride, become inexcitable. 
§ 127. Elimination. —The potassium salts appear to leave the body through the 
kidneys, but are excreted much more slowly than the corresponding sodium salts. 
Thus, after injection of 4 grins, of potassic chloride, in the first sixteen hours 
•748 grm. of KC1 was excreted in the urine, and in the following twenty-four hours 
2-677 grms. 
§ 128. Nitrate Of Potash (KNOg).—Pure potassic nitrate crystallises in large 
anhydrous hexagonal prisms with dihedral summits ; it does not absorb water, and 
does not deliquesce. Its fusing point is about 340° ; when melted it forms a trans¬ 
parent liquid, and loses a little of its oxygen, but this is for the most part retained 
by the liquid given off when the salt solidifies. At a red heat it evolves oxygen, 
and is reduced first to nitrite ; if the heat is continued, potassic oxide remains. The 
specific gravity of the fused salt is 2-06. It is not very soluble in cold water, 100 
parts dissolving only 26 at 15-6°; but boiling water dissolves it freely, 100 parts 
dissolving 240 of the salt. 
A solution of nitrate of potash, when treated with a zinc couple (see Foods, 
p. 525), is decomposed, the nitrate being first reduced to nitrite, as shown by its 
striking a red colour with metaphenylene-diamine, and then the nitrate further 
decomposing, and ammonia appearing in the liquid. If the solution is alkalised, 
and treated with aluminium foil, hydrogen is evolved, and the same effect produced. 
As with all nitrates, potassic nitrate, on being heated in a test tube with a little water, 
some copper filings, and sulphuric acid, evolves red fumes of nitric peroxide. 
§ 129. Statistics. —Potassic nitrate, under the popular name of “ nitre ,” is a 
very common domestic remedy, and is also largely used as a medicine for cattle. 
There appear to be at least twenty cases of potassic nitrate poisoning on record : of 
these, eight were caused by the salts having been accidentally mistaken for magnesic 
sulphate, sodic sulphate, or other purgative salt; two cases were due to a similar 
mistake for common salt. In one instance, the nitrate was used in strong solution 
as an enema, but most of the cases were due to the taking of too large an internal dose. 
§ 130. Uses in the Arts, etc. —Both sodic and potassic nitrates are called 
“ nitre ” by the public indiscriminately. Sodic nitrate is imported in large quantities 
from the rainless districts of Peru as a manure. Potassic nitrate is much used in 
the manufacture of gunpowder, in the preservation of animal substances, in the 
manufacture of gun-cotton, of sulphuric and nitric acids, etc. The maximum 
medicinal dose of potassium nitrate is usually stated to be 30 grains (1-9 grm.). 
§ 131. Action of Nitrates of Sodium and Potassium. —Both of these salts are 
poisonous. Potassic nitrate has been taken with fatal result by man ; the poisonous 
nature of sodic nitrate is established by experiments on animals. The action of the 
nitrates of the alkalies is separated from that of the other neutral salts of potassium, 
etc., because in this.case the toxic action of the combined nitric acid plays no insigni¬ 
ficant part. Large doses, 3-5 grms. (46-3-77-2 grains), of potassic nitrate cause 
considerable uneasiness in the stomach and bowels ; the digestion is disturbed ; 
there may be vomiting and diarrhoea, and there is generally present a desire to 
urinate frequently. Still larger doses, 15-30 grms. (231-5-463 grains), rapidly 
produce all the symptoms of acute gastro-enteritis—great pain, frequent vomiting 
(the ejected matters being often bloody), with irregularity and slowing of the pulse ; 
