CHEMISTRY. 



J '35 



'.tr; but is perfectly insoluble in alcohol. When 

 b'-irnt, it emits the cdcnir of carorr.el, and exhibits precise- 

 ly the appearance of burning sugar. When distilled, it 

 yiflds the same products as sogar, only the empyretima- 

 t;c oil obtained has the odour of benzoic acid. When 

 treated with nitric acid, it yield saclactic acid. From 

 these experiments, it appears that sugar of milk is spe- 

 cifically different from every kind of vegetable sugar at 

 present known. Its constituents, according to the ex- 

 periments of Thenard and Gay-Lussac, are as follows : 



Oxygen 53.83+ 



Carbon 38.82.5 



Hydrogen 7.311 



100 



2. Honey is prepared by bees, and perhaps rather be- 

 longs to the vegetable than the animal kingdom. It hag 

 a white or yellowish colour, a soft and grained consist- 

 ence, a saccharine and aromatic smell. By distillation 

 it affords an acid phlegm and an oil, and it? coal is light 

 and spongy like that of the mucilages of plant*. Nitric 

 acid extracts from it oxalic acid, precisely as it does 

 from sugar. It is very soluble in water, with which it 

 forms a syrup, and like sugar passes to the vinous fer- 

 mentation. 



According to Proust, there are two kinds of honey ; 

 one always liquid, and the other solid and not deliques- 

 cent. They may be separated, he says, by means of 

 alcohol. 



3. The urine of persons labouring under the disease 

 known to physicians by the name of diabetes, yield*, 

 when evaporated, a considerable quantity of matter which 

 possesses properties analogous to sugar. This seems to 

 have been first observed by Willis. When treated with 

 nitric acid, it yielded the same proportion of oxalic acid 

 as aa equal quantity of common sugar would have done, 

 making allowance for the saline substances present. No 

 saclactic acid was formed. Hence it follows, that this sub- 

 stance is not analogous to sugar of milk, but nearer com' 

 mon sugar in its properties. It has been supposed inca- 

 pable of crystallizing regularly like common sugar. But 

 we have seen it prepared by Dr Wollaston m small 

 grains, having almost exactly the appearance of common 

 white sugar. 



SECT. VII. Of Oils. 



The oily substances found in animals belong all to the 

 class of fixed oils. They differ very much in their con- 

 sistence, being found in every intermediate state, from 

 spermaceti, which is perfectly solid, to train oil, which 

 is completely liquid. The most important of them are 

 the following : 



1. Spermaceti. This peculiar oily substance is found 

 in the cranium of the physeter macrocephalus, or sperma- 

 ceti whale. It is obtained also from some other species. 

 At first it is mixed with some liquid oil, which is separated 

 by means of a woollen bag. The last portions are re- 

 moved by an alkaline ley, and the spermaceti is after- 

 wards purified by fusion. Thus obtained, it is a beauti- 

 ful white substance, usually in small scales, very brittle, 

 has scarcely any taste, and but little smell. It is distin- 

 guished from all other fatty bodies by the crystalline 

 appearance which it always assumes. It melts, accord- 

 ing to the experiments of Bostock, at the temperature 

 of 112. When sufficiently heated, it may be distilled 

 over without much alteration ; but when distilled re- 

 peatedly, it lox* its tobd form, and becomes a liquid 

 oil. 



2. Fat. This substance is found abundantly in diffe- Chemical 



rent parti of animals. When pure, it possesses the pro- Eomina- 



i- ,<-, T > r i i tion oi 



perties of the fixed oils. Its consistence vanes trom tal- jf ature . 



low or sucl, which is brittle, to hog's lard, which is soft ^^-j-^s 



and semi-fluid. To obtain fat pure, it is cut in small Fat. 



pieces, well washed in water, and the membranous parts 



and vessels separated. It is then melted in a shallow 



vessel along with some water, and kept melted till tlie 



v.-au-r is completely evaporated. Thus purified, it is 



white, tasteless, and nearly insipid. 



i>. Train oil. This liquid is extracted from the blub- Train oil. 

 bet- of the whale, and fn;m other fish. It forms a very 

 important article of commerce, being employed for com- 

 bustion in lamps,. and for other purposes. It is at first 

 thick; but, on standing, a white mucilaginous matter is 

 deposited, and the oil becomes transparent. It is then 

 of a reddish brown colour, and has a disagreeable smell. 



4". Though all the oily bodies found in animal sub- Animal oil 

 stances belong to the etas of fixed oils, yet there is a pe- of Dippcl. 

 culiar volatile oil which makes its appearance, and which 

 is doubtless formed during the distillation of different. 

 animal bodies. Though this oil has now lost that cele- 

 brity which drew the attention of the older chemists to 

 it, yet, as its properties are peculiar, a short account of 

 it will not be improper. It it usually called the aiiinut? 

 oil of Dijipel, because that chemist first drew the atten- 

 tion of chemists to it. It is usually obtained from the 

 gelatinous and albuminous parts of animals. The horns 

 are said to answer best. The product of the first distil- 

 lation is to be mixed with water, and distilled with a 

 moderate heat ; the oil which is first obtained is the ani- 

 mal oil of Dippel. 



It is colourless and transparent ; its smell is strong 

 and rather aromatic ; it is almost as light and as vola- 

 tile as ether ; water dissolves a portion of it ; and it 

 changes syrup of violets green, owing, as is supposed, to 

 it* containing a little ammonia. The acids all dissolve 

 it, and form with it a kind of imperfect soap. Nitrous 

 acid sets it on fire. It forms with alkalies a soap. Al- 

 cohol, ether, and oils, unite with it. When exposed to 

 the air it becomes brown, and loses its transparency. It . 

 was formerly used as a specific in fevers. 



r. VIII. Of Animal Resins. 



Substances resembling resins are found in different ani- Animal 

 mal bodies, and which, for that reason, may be called retiiu, viz. 

 animal resins. Their properties arc somewhat different 

 from the vegetable resins, but they have not been all ex- 

 amined with precision. The following are the most re- 

 markable of these substances. 



1. Resin qfiile. This substance may be obtained by Resin of 

 the f Mowing process : Into thirty two parts of fresh ox bile, 

 bile puur one part of concentrated muriatic acid. After 

 the mixture has stood for some hours, pass it through a 

 filter, in order to separate a white coagulated substance. 

 Pour the filtrated liquor, which has a fine green colour, 

 into a glass vessel, and evaporate it by a moderate heat. 

 When it has arrived at a certain degree of concentration, 

 a green coloured substance precipitates. Decant off the 

 clear liquid, and wash the precipitate in a small quantity 

 of pure water. This precipitate is the kuit of bile, or 

 the resin (t/'lite, as it is sometimes called. 



The resin of bile is of a dark brown colour ; but when 

 spread out upon paper or on wood it is a fine grass green. 

 Its taste is intensely bitter. 



When heated to about 122 it melts; and if the heat 

 be still farther increased, it takes fire and burns with ra- 



