116 



CHEMISTRY. 



other impurities which the hyposulphite will 

 not remove ; these are of a more stable char- 

 acter, and, as they possess a higher boiling- 

 point than chloroform, they may be separated 

 by distillation, or by treatment with sulphuric 

 acid in the usual manner. 



Etching on Copper. A new process for en- 

 graving on copper consists of the following 

 steps: 1. The copper-plate is covered with a 

 layer of adherent silver, on which a colored 

 varnish is spread. 2. The design is sketched 

 upon this with a dry paint. 3. Perchloride of 

 iron is then applied, which bites in the lines 

 of the design. 



Formation of Urea in the Organism. Though 

 it has been supposed by many chemists that 

 urea is a direct product of the gradual oxida- 

 tion of albumin, all attempts at its artificial 

 production have hitherto failed. The products 

 obtained by the use of oxidizing agents have 

 been ammonia, benzoic acid, and aldehydes of 

 the fatty series, while those obtained by the 

 use of acids and alkalies have been ammonia 

 and amido-acids of the fatty and aromatic se- 

 ries (glycocine, leusine, and tyrosine). In the 

 living organism, whenever albumin is decom- 

 posed and oxidation is hindered by the absence 

 of haemoglobin, as in the case of pus, much 

 leusine and tyrosine are found, but little or no 

 urea. So, too, when the oxidizing power of 

 the organism is diminished these principles ap- 

 pear in the urine, but hardly any urea. Two 

 German chemists, Messrs. Schultzen and Nen- 

 cki, reasoning from these facts, were led to be- 

 lieve that the amido-acids of the fatty series, 

 and perhaps tyrosine, are the intermediate 

 links between albumin and urea. To test this 

 hypothesis, they fed dogs on a diet containing 

 a constant but small amount of nitrogen, and 

 thus got a constant and small amount of nitro- 

 gen in the urine. Then they administered a 

 quantity of leusine and glycocine, the result 

 being a large increase of urea, the nitrogen in 

 this additional urea corresponding with that 

 of the glycocine and leusine. Thus it was 

 proved that these bodies are converted into 

 urea. Tyrosine also increased the urea, though 

 not to so great an extent, and part of it re- 

 mained unchanged in the urine and fteces. 

 Acetamide was excreted unchanged. As ami- 

 do-compounds analogous to acetamide are not 

 excreted normally, they probably are not 

 formed during the decomposition of albumin in 

 the body. Since amido-acids contain only one 

 atom of nitrogen and .urea contains two, it 

 must be formed from them by synthesis, and 

 the authors think it likely that bodies from 

 the cyanogen group form the intermediate 

 links. It is supposed that the albuminous 

 substances contained in food take up water 

 under the influence of the digestive ferments, 

 and are split up, partly in the alimentary canal 

 but chiefly in the circulation, into amido-acids 

 and non-nitrogenous bodies. The latter under- 

 go combustion, yielding carbonic acid and 

 water, while the amido-acids form urea. The 



authors think it not improbable that ammonia 

 is liberated from albumin simultaneously with 

 cyanic acid and unites with it to form urea, or 

 with cyanogen to form cyanamide, which is 

 then transformed into urea. 



Tempering Steel. An improvement in this 

 process, suggested by H. Caron, consists in heat- 

 ing the water into which the steel is plunged. 

 A temperature of about 55 0. is sufficient to 

 give to the spiral springs of the needle-gun 

 an elasticity and resistance corresponding to 

 the best ordinary tempering followed by the 

 usual drawing. Steel containing from .002 to 

 .004 of carbon, tempered in boiling water, has 

 its tenacity and elasticity greatly increased, 

 without sensibly altering its softness. For re- 

 generating burned iron, Caron employs a boil- 

 ing solution of chloride of sodium. A bar of 

 burned iron, which, before this tempering, 

 broke without bending, was, after the bath, 

 capable of being bent double in the cold. 



New Coloring-Matters. A process for con- 

 verting certain organic bodies into coloring- 

 matters has been patented in France by Messrs. 

 Croissant and Bretonniere. The substances em- 

 ployed are mostly of little intrinsic value, such 

 as sawdust, humus from old trees, mosses, cel- 

 lulose, horn, etc. Starch, horn, tannin, and 

 aloes, are also among the substances which are 

 converted into coloring-matters. The prin- 

 ciple involved is the dehydrogenation of the 

 bodies by the action of sulphur at a high tem- 

 perature, the sulphur being supposed to replace 

 the hydrogen. If, for instance, it be required 

 to convert bran into coloring-matter, it is placed 

 in a small sheet-iron tank fitted with a lid. 

 Caustic soda and flowers of sulphur are added 

 in certain proportions, and the whole is made 

 up into an homogeneous paste. The vessel 

 is then placed in a furnace where it can be 

 heated to from 256 to 300 C. Sulphuretted 

 hydrogen is given off in abundance. When the 

 mixture is dry, we find in the boiler, after cool- 

 ing, a black, friable matter, perfectly soluble in 

 water, to which it imparts a fine sap-green. The 

 solution has a strong affinity for fibres, which 

 it dyes without mordant. One and the same 

 body gives various tones of color, according to 

 the temperature and the proportions of the 

 mixture. Certain substances, such as extracts 

 of dye r woods, aloes, etc., are converted at 

 boiling-point ; while lignine, bran, etc., require 

 a higher temperature. The following examples 

 are added : 



(1.) Aloes 3 kilogrammes. 



Caustic-soda lye at 40 Beaume. 10 litres. 



Water 10 " ' 



Flowers of sulphur 3 kilogrammes. 



The mixture is boiled, and yields a lilac-gray. 

 At higher temperatures a deep brown is pro- 

 duced. 



(2.) Humua 20 kilogrammes. 



Normal sulphide } 40 litres. 



This " normal sulphide " contains 70 litres 

 soda-lye at 40 Beaume, 65 litres of water, and 

 30 kilogrammes of sulphur. To dye cotton, a 



