Page images
PDF
EPUB

.

[ocr errors]
[ocr errors]
[ocr errors]

.

[ocr errors]
[ocr errors]

.

.

.

hydrochloric acid, and the sulphuric acid precipitated by chloride of barium, gave 1.204 grm. sulphate of baryta. The substance employed was dried in vacuo. In 100 parts,

I.

II.
Carbon

8:44 8:44
Hydrogen

2:16 2:17
Sodium

16.09 16.04
Oxygen
Sulphurous acid

45.40 These numbers lead to the formula

2(Na HO, SO2), Co H4 03*, according to which the substance ought to containCarbon

2 24 8.45 Hydrogen

6 6 2:11 Sodium

2 46 16:19 Oxygen

5 80 28.16 Sulphurous acid 2 128 45.09

284 100.00 I have to thank Prof. von Liebig for kindly permitting me to execute the above analytical determinations in his laboratory, whilst I was staying in Germany during last midsummer vacation.

From the compound 2(Na HO, SO2), C? Ho 03, the glyoxal cannot be separated by addition of carbonate of soda, so as to neutralize the salphurous acid completely. Even if not sufficient carbonate of soda is added, and the 2(Na HO, SO2), Co H*08 is left in excess, the liquid turns dark brown, which colour increases on application of heat, and gradually a dark precipitate falls down.

The reason of this is, apparently, the formation of a new kind of sulphur compound from the glyoxal. The latter by itself alone is altered in a very different manner by contact with alkaline substances, as I shall show presently.

Glyoxal with bisulphite of ammonia, C? H(NH4)2 03, 280?.

A strong solution of bisulphite of ammonia mixed with glyoxal deposits very soon a large quantity of beautiful crystals of the above compound; at the same time a considerable evolution of heat takes place. One or two crystallizations from boiling water are sufficient for its purification. In effecting this object, if the boiling is continued too long, the solution acquires a yellow colour, and the compound is partly decomposed.

It crystallizes in prisms of great lustre, which dissolve easily in water, but are almost entirely insoluble in alcohol. The aqueous solution is precipitated by acetate of lead, but not by salts of copper, zinc, or silver.

* S=32.

[ocr errors]
[ocr errors]

...

.

.

.

.

.

...

[ocr errors]

Analysis gave the following results :

I. 0.799 grm., dried in vacuo and burnt with chromate of lead, gave 0.297 grm.

carbonic acid and 0.326 grm. water. II. 0:56 grm., burnt with chromate of lead, gave 0-202 grm. carbonic acid and 0·226 grm, water.

0:739 grm., boiled with a mixture of chlorate of potash and hydrochloric acid, gave 1:42 grm. of sulphate of baryta. In 100 parts, –

I.

II.
Carbon

10.13 9.83
Hydrogen

4:53 4.48
Oxygen
Nitrogen
Sulphurous acid

52.8 From these numbers I can only calculate the formula

Co Ho (NH4)* 0°, 2SO,
which requires,-
Carbon

2 24 10.0
Hydrogen
10 10

4:20
Oxygen

3 48
Nitrogen

2 28
Sulphurous acid 2 128 53.7

238 The composition of the above compound is analogous to the corresponding one of the aldehyde of acetic acid,

Co Ho (NH4)2, SO3. There is but this difference, that the common aldehyde contains only one atom of hydrogen which can be replaced by electropositive or negative radicals, whilst the glyoxal contains two atoms of hydrogen of this character. It corresponds to the bibasic acids.

If a cold solution of chloride of barium is mixed with a concentrated solution of 2(Na HO, SO?), C? H4 03 in about equivalent quantities, and the clear mixture is allowed to stand quietly for two or three days, a hard crystalline crust of a compound of Glyoxal with bisulphite of baryta, 2(C? H’Ba? 03, 280?) +7H’O, collects at the bottom of the basin. It can easily be purified by recrystallizing it once or twice from boiling water. This compound forms small white crystals, sparingly soluble in cold, but easily in hot water. The aqueous solution becomes turbid on continued boiling, and smells a little like sulphurous acid. The

a solid compound, heated on platinum foil, turns black, emits sul

[ocr errors]
[ocr errors]

.

.

.

[ocr errors]

.

[ocr errors]

phurous acid, burns, and is converted into white sulphate of baryta.

The analysis of this compound gave the following results :

I. 0·787 grm., burnt with chromate of lead, gave 0·177 grm. carbonic acid and 0.160

grm.

water. 0.379 grm., dissolved in water and precipitated with sulphuric acid, gave 0·219 grm. of sulphate of baryta.

0-340 grm., oxidized with a mixture of chlorate of potash and hydrochloric acid, and the sulphuric acid precipitated by chloride of barium, gave 0.390 grm. of sulphate of baryta.

II. 0.705 grm., burnt with chromate of lead, gave 0·158 grm. carbonic acid and 0.139 grm, water.

0·432 grm., burnt in a crucible, moistened with sulphuric acid, left, after the excess of the latter had been expelled by application of heat, 0.250 grm. of sulphate of baryta.

The substance employed was dried in vacuo, and according to the above determinations, contains in 100 parts,

I.

II.
Carbon .

6:13 6:11
Hydrogen

2.25 2:19 Barium

33.77

33.98
Oxygen .

Sulphurous acid 31:53
The formula 2(C2H? Ba? 09, 2804) +7H'O requires,
Carbon

4 48 5.97
Hydrogen

18 18 2.25 Barium

4 274 34.07 Oxygen

13 208 25.87 Sulphurous acid. 4 256 31.84

804 100.00

Glyoxal, CH40%. The compound of glyoxal with bisulphite of baryta is dissolved in boiling water, and to this solution diluted sulphuric acid added as long as a precipitate of sulphate of baryta is produced. The filtrate from the latter contains sulphurous acid and glyoxal,C2H2Ba , 2802+H HO, SOS=C2H408 + Ba’O SO3 +2502.

Glyoxal. Sulphate of

baryta. On evaporating at first on the water-bath and afterwards in vacuo, or in a stream of carbonic acid, the sulphurous acid and water go off, and the glyoxal remains as an amorphous, transparent, and nearly colourless substance. It absorbs moisture very readily from the air, and dissolves in water, alcohol, and æther. The aqueous solution precipitates acetate of lead very

...

.

.

.

.

.

[ocr errors]
[ocr errors]
[ocr errors]
[ocr errors]

slightly, but on addition of ammonia a strong white precipi. tate falls down. Nitrate of silver and ammonia mixed with the same solution precipitated, on application of heat, a very bright and strong coating of metallic silver on the sides of the test-tube. Sulphuretted hydrogen acts upon the glyoxal, and it is

very probable that merely an interchange of sulphur and oxygen between both substances takes place.

Sulphuretted hydrogen does not act on the isomeric glycolic acid. Glycolate of lead was decomposed by sulphuretted hydrogen, and after filtration the excess of the latter expelled by heat. The remaining acid, on being neutralized with carbonate of lime, gave only crystals of glycolate of lime, which did not contain a trace of sulphur.

Caustic potash, lime, or baryta, convert the glyoxal into glycolic acid,

Co H* 0°+Ca H2=C Ho CaO+HoO.

Glyoxal. A quantity of crude glyoxal was boiled with carbonate of lime. The latter did not dissolve, and the filtrate again furnished on evaporation all the glyoxal employed, with its peculiar qualities.

Glycolic acid decomposes with the greatest facility carbonate of lime, producing glycolate of lime.

Some crude glyoxal, prepared as described in the beginning of this paper, was mixed with slaked lime and water till a slight alkaline reaction became perceptible. After removing the excess of lime by means of carbonic acid, the filtrate furnished to the last drop only crystals of glycolate of lime. The precipitate of carbonate of lime dissolved almost entirely in carbonic acid water, and was on boiling again completely precipitated; therefore no oxalate of lime or any other similar substance had been produced.

A quantity of the compound of glyoxal with bisulphite of baryta was dissolved in boiling water, and caustic baryta added till the liquid became alkaline. It now contained a precipitate of a slight yellow colour, which proved to be only sulphite of baryta, (Ba’O, SO2). The filtrate from the latter was freed from baryta by means of diluted sulphuric acid. The acid liquid thus obtained gave, after neutralization with carbonate of lime, only crystals of glycolate of lime. The latter was recognized by the characteristic shape of its crystals and by the amount of water of crystallization. 0.370 grm., dried in vacuo, lost at 100° C. 0.080 grm. water. Consequently 100 parts contain :

21.62. The formula 2(C2H% Ca09) + 3H'O requires

22.1 of water of crystallization. The decomposition of the glyoxal-bisulphite of baryta by baryta

is therefore expressed by the following equation :
2(C2 H2 Ba? 03, 2802) +7H20 +6Ba HO

Baryta.
=4Ba’O SO2 +9H HO +2C2 H3 Ba03.

HO+
Sulphite of

Glycolate of
baryta.

baryta. The conversion of the latter into glycolate of lime was preferred on account of the greater facility with which it crystallizes.

The caustic alkalies therefore convert the glyoxal into glycolic acid. But if, before adding the alkaline substance, a soluble bisulphite has been mixed with glyoxal, a different decomposition takes place. The liquid turns brown, and soon a dark precipitate subsides.

Some glyoxal was heated with potassium. No cyanide of potassium could be detected in the burnt mass; therefore glyoxal does not contain nitrogen. Since glyoxal unites with bisulphites of soda, ammonia, and baryta, I examined the capabilities of glycolic acid in this respect. Some of the latter substance, of about the consistency of strong syrup, was mixed with bisulphite of soda. No crystals were formed after one week's standing, although in the case of glyoxal this took place within two or three hours after the preparation of the mixture. It has also been shown that the compound of glyoxal and bisulphite of soda turns brown on addition of caustic potash. On adding the latter to the mixture of glycolic acid and bisulphite of soda, no change in colour was produced.

Crude glyoxal was dissolved in water, a little diluted nitric acid added, and then evaporated on the water-bath till all the nitric acid had been expelled. A residue of a strong acid reaction remained, which on being neutralized with chalk gave cry. stals of glyoxylate of lime, (C? Ho CaO4). This salt could easily be recognized by the shape of its crystals, and its characteristic behaviour with lime-water.

Co H+ 03 + N HO = Co H+ + N HOo.

Glyoxal. Nitric acid. Glyoxylic acid. Nitrous acid. Glyoxal, prepared from its compound with bisulphite of baryta, furnished the same result on being heated with diluted pitric acid. An excess of nitric acid converts the glyoxal into oxalic acid,

CH4 08 + 2NHOS = CPH 04 + H2O+2NHO.

Glyoxal. Nitric acid. Oxalic acid. Glycolic acid dissolved in water and treated with nitric acid in a similar manner did not furnish any glyoxylic acid, but was converted partially into oxalic acid.

« PreviousContinue »