CHAPTER VI. 



AMMONIA— AMMONIUM SULPHIDE— AMMONIUM SULPHOCYANIDE— AM- 

 MONIUM SULPHATE — AMMONIUM CARBONATE — SODIUM HYPO- 

 SULPHITE—SODIUM SULPHATE — SODIUM CHLORIDE (COMMON 

 SALT)— SODIUM NITRATE (CHILI SALTPETRE) — ARSENITE OF 

 SODA— BORAX— SODIUM CARBONATE. 



1 8. Ammonia, NH3. — Preparation. — By distilling ammonical gas 

 liquor or fermented urine with lime. 



Properties. — Ammonia is a colourless gas with a pungent smell, 

 which irritates the mucous membranes, and an acrid taste. Aqueous 

 solutions are met with in commerce, as liquor ammoniac, containing 

 about 30 per cent of ammonia gas. Such solutions rapidly alter in 

 the air by the evaporation of the dissolved gas. Owing to its causticity 

 ammonia is employed in medicine as a rubefacient, or to induce 

 vesication. Ammonia is one of the nutritive substances of the plant, 

 and its presence in the air greatly stimulates the growth of the latter. 

 Normally the air does not contain more than 0*056 milligramme of am- 

 monia per cubic metre, but this dose varies much. The amount varies 

 according to the altitude : at 395 metres, 0-9 to 2*76 milligrammes ; 

 at 1446 metres, 3-18 milligrammes ; and at 1884 metres, 5-5 milli- 

 grammes. The dose injurious to plants is about 1000 times gi-eater 

 than the normal dose. Some plants are more sensitive than others 

 (Meyer). Whilst 243 milligrammes of ammonia per cubic metre 

 of air had no bad effect on oaks, even if they remained an hour in that 

 atmosphere, 70-86 milligrammes caused a pathological condition on 

 plum-trees and cherry-trees. A dose of 32-36 milligrammes of ammonia 

 per cubic metre has no caustic action on the most sensitive of vege- 

 tables. The symptoms of burning by ammonia are the following : The 

 leaves of the oak blacken ; those of cherry-trees and plum-trees become 

 brown ; haricots blacken ; and cereals lose their colour and become 

 quite pale. Young buds are much more sensitive than old leaves. A 

 0-003-0-005 per cent solution has no action on the protoplasma of 

 maize, haricots, tomatoes, and strawberry plants ; more concentrated 

 solutions inci-ease the movements of the protoplasma. 



The seeds of Phaseolus multiflora germinate in nine days in an 

 atmosphere containing 0-003-0-004 per cent of ammonia ; likewise the 

 seeds of Viciafaha, when the ambient air contains 0-0031 per cent of 

 this gas. In an atmosphere containing 0*005 per cent of ammonia 

 leguminous seeds cannot germinate, and a 0'0083 per cent solution 

 exercises an unfavourable action on young maize, owing to its 

 diminished growth. 



Use. — The causticity of ammonia being known, it is evident that 

 (98) 



