A R S

ASP

( 66 )

of the arsenious acid which is 34.263. Theseconditions will be fulfilled (making a reason-able allowance for errors) by taking the oxygenin 100. parts of arsenic acid as double that ofthe sub-oxyd of lead with which it is saturated,that is, 16.9S1 X 2 r= 33.962.

Arsenic acid will therefore contain,

Arsenic. . 66.038 — 100Oxygen . 33.962 — 51.428

100.000 — 151.428

And as the arsenious acid contains 34.263oxygen to 100. of metal, the arsenic acid willcontain to the same quantity of metal J f times34.263 51.3945, within a very small dif-

ference.

It has been already mentioned, under thearticle affinity, that wherever the ratio betweentwo portions of the same substance that uniteto another substance is expressed by a fraction(as 1there is reason to suppose some minimumof combination which will convert these frac-tional numbers to integers. This in the presentinstance will be produced by assuming theminimum of oxydation of arsenic, as eitherhalf or a quarter of that of the arsenious acid.It is well known that when metallic arsenic isexposed to the air it loses its lustre and becomescovered with a blackish brown powder. Theauthor exposed 200. parts of metallic arsenicfor two months to the air, at the end of whichtime it entirely fell into a bulky black powder.The increase of weight in that time was 16,2,and in another month the further increase wasonly 0.75, being in all 16.95, or in the propor-tion of 8.475 oxygen to 100. of metal, and8.475 X 0 = 50.85, which does not muchdiffer from 51.428, the highest term of oxyge-nation. Hence it is probable that the arseniousacid is 4 times the minimum of oxygenation,and the arsenic acid 6 times.

The Arsenile of Lead, mentioned above hasthe following properties: when dry it is white,and by friction it becomes apparently evenmore electric than sulphur. When melted itis transparent, and remains so after coolingand then becomes yellowish, but of a darkgreen if any copper is present. Arsenite oflead kept at a red heat gives out arsenious acid,and is gradually changed to arseniate of lead.

Arsenicaled Hydrogen.

Under the article Aik aline Hasis in thisappendix we have mentioned the alloy ofpotassium and arsenic, and the production of

arsenicatcd hydrogen by adding water to thisalloy. It was there found that when 100parts of arsenicated hydrogen are kept in contactwith melted tin, the latter extracts all thearsenic and then the hydrogen expands to 140parts. ( See the above article.)ASPARAGUS.

The juice of this plant has been examinedwith much care and skill by M. Robriquet. 3A quantity of asparagus was first bruised andthe juice extracted by pressure, and passedthrough a coarse cloth, leaving a fecula behind.The juice in this state had a strong unpleasantsmell, and was a dirty yellow colour incliningto green. The fecula, treated by boiling alcohol,only partially dissolved, and the insoluble-por-tion examined in various ways strongly re-sembled animal gluten, in drying to a hornymass which by combustion gave much ammonia.The part soluble in hot alcohol deposited on cool-ing a substance a good deal like wax ; whilst thesupernatant solution contained a species of resin.

The filtered recent asparagus juice was sen-sibly acid and reddened litmus. After boiling,to separate some remaining flocculi of albumen,it was evaporated nearly to dryness, and thendigested with alcohol, and the part untouchedby this agent was dissolved in water. Thealcoholic solution gave a very slight precipitatewith acetite of lead, and this metallic precipitate-was not again soluble in distilled vinegar, thusshewing that the acid of the asparagus-juicewas not the malic. Another portion of thejuice was assayed by distillation with sulphu-ric acid, and a quantity of acetic acid unitedwith potash was obtained. Still the acid ofthe juice was not clearly made out, and it wasafterwards analyzed with great attention. Toobtain it pure the expressed juice of the plantwas first coagulated by heat, and the clearliquor filtered. Into this liquor was poured 1acetite of lead as long as any precipitate formed,,and this last when well washed was digestedwith a third of its weight of sulphuric aciddiluted with three parts of water, and mode-rately heated. The sulphat of lead thus formedremained at the bottom, and the clear super-natant liquor was evaporated to an extractive-consistence, and treated with alcohol twice-successively (excluding a little insoluble mattereach time) till a clear solution in the spirit wasobtained. This acid was brownish, had avery sour- taste mixed with some unpleasantflavour particularly when heated,, and gavesoluble salts with the alkalies and insoluble

3 An. Chim. tom. 55 .