(' II K M I S T R V. 



let proper- 



Suberic 

 acid. 



In proper- 



MM. 



ing the precipitate in a sufficient quantity of sulphu- 

 ric icid to separate the lead, mid then filtrating. The 

 liquid contained pure malic aciil. 



When malic acid in obtained by the action of nitric 

 acid on sugar, it is colourless ; but it very easily ac- 

 quires a brown colour by the Action of heat, or even 

 by keeping it in a liquid state. When evaporated, 

 it may be obtained in a solid state ; but it is not ca- 

 pable of crystallizing. Its taste is very acid, and it 

 dissolves readily in water. It is said to undergo 

 spontaneous decomposition ; but we have kept it 

 more than two years in a liquid state without obser- 

 ving any such change. It bears a strong resemblance 

 to the citric acid, but it does not crystallize ; forms 

 more soluble salt with lime ; and precipitates mer- 

 cury, lead, and silver, from nitric acid, which citric 

 acid does not. 



The compounds which it forms with the salifiable 

 bases, are called malaiet. 



SECT. XV. Of Suberic' Acid. 



This acid was obtained by Brugnatclli by digest- 

 ing common cork in nitric acjd. Its properties 

 were afterwards more investigated by Bouillon La 

 Grange. 



It does not crystallize, but may be obtained in 

 powder or in pellicles. Its taste is acrid and slight- 

 ly bitter ; it reddens vegetable blues, attracts mois- 

 ture when exposed to the air, but is not very soluble 

 in water. It may be sublimed without decomposi- 

 tion. The other acids dissolve it incompletely. The 

 salts which it forms are called suit-rales. 



SECT. XVI. Of Formic Acid. 



This acid exists in the formica rufrt, or red ant. 

 It- was noticed in a paper by Mr Ftay in 1671, in 

 consequence of the observations of Halse and Fisher. 

 But its properties were first investigated by Mar- 

 graff. Fourcroy and Vauquelin endeavoured to 

 prove that it was a mixture of acetic and malic" 

 acid*; but the experiments of Suersen have shewn 

 that this opinion is not correct. 



This acid may he obtained by infusing the ants in 

 water, distilling, off the water as long as it -come* over 

 without any burnt smell, saturating the water with- 

 potash, evaporating to dryness, mixing the residue 

 with as much diluted sulphuric acid as is sufficient to 

 saturate the potash employed, distilling this mix- 

 ture to dryness, rectifying the liquid that comes over 

 by a second distillation with a moderate heat. The 

 liquid now contains only pure formic acid, 

 tit proper- This liquid is colourless like water. It has a pe- 

 ties. culiar smell ; it reddens vegetable blues, and has an 



acid taste. Its specific gravity varies from 1.102-to 

 1.113, whereas the most concentrated acetic acid is 

 only 1.O80 Notwithstanding this superior weight, it 

 is not capable of neutralizing so much of the salifia- 

 ble bases as acetic acid. Lowitz attempted, in vain, 

 to procure this acid in crystals, though he succeeded 

 easily with acetic acid. The compounds which it 

 form* with the different bases are called formates. 

 Th're is a striking analogy between tliem and the 

 aetialcs. 



('ormic 



How ob- 



CHAP. VI. 



Of Colorific Adds. 



this name we include three substances, Colorific 

 which possess such peculiar properties that they 

 outfht to be coiuidered separately from the combus- 

 tible acids. These are. prttwic aciil, gallic acid, and 

 tannin. The two first have always been considered- 

 as acids. The last, though not acid, is so intimately 

 connected with the gallic, that tlu-y cannot well be 

 separated. These substances posses* the following- 

 characters. 



1. They unite with alkaline bodies, but do not 

 seem capable of neutralizing them. 



2. They act with great energy upon metallic so- 

 lutions, usually entering into combination with thcs 

 oxide, and precipitating it 4n the tte of an insoluble 

 powder. 



3. They have a tendency to enter into triple com- 

 pounds with a variety of bodies, especially with me- 

 tallic oxides and alkalies. 



SECT. I. Of Triune Acid. 



This important substance was accidentally disco- 

 vered by a chemist of Berlin in 1710. This chemist, cid - 

 Diesbach by name, found out the method of prepa- 

 ring Prussian blue. The nature of this pigment was 

 examined by Brown. But it was Macquer who first 

 ascertained its nature in a satisfactory manner. In 

 consequence of his experiments, Prussian blue was 

 considered as a compound of oxide of iron, with a 

 peculiar acid. But no one was able to obtain this 

 acid in a separate state, or to ascertain its proper- 

 ties, till Scheele, in two admirable dissertations pub- 

 lished in l~H'2 and 17SJJ, pointed out a method 

 of procuring it, and gave a detailed account of its 

 nature. 



He procured the Prlissic acid in the following How ob- 

 manner : He boiled in a matrass a mixture of 10 tained. 

 parts Prussian blue, 5 parts red oxide of mercury, 

 and .SO parts of water, and filtered the solution. The 

 liquid was poured upon 2\ parts of clean iron filings, 

 and at the same time 1 part of sulphuric acid was 

 added, and the mixture shaken. The iron disappear- 

 ed, and a quantity of running mercury was precipi- 

 tated in its place. Distil off one-fourth of this liquid 

 by a moderate heat, what comes over consists of wa- 

 ter holding prussic acid in solution. 



Prussic acid, thus obtained, is a colourless liquid It proper- 

 like water. It has a strong odour, resembling that tlc *- 

 of the flowers of the peach or of bitter almonds. Its 

 taste is sweetish, acrid, and hot, and it is apt to ex- 

 cite cough. It does not alter the colour of vege- 

 table blues. When swallowed, it proves a very viru- 

 lent poison. 



In this state it is combined with water ; but Gay- How ok- 

 Lussac obtained it pure by the following process : umed 

 He put into a tubulated rct.jrt a quantity of prussi- P U1C - 

 ate of potash, and poured over it weakly fuming 

 mur.atu- acid. The retort was luted to a flask con- 

 taining a mixture of. chalk and muriate of lime in 

 powder. This flask communicated with a second 



