122 



CHEMISTRY. 



ginally non-precipitable after their solutions 

 have been treated with caustic alkalies or strong 

 acids, find their explanation in the properties of 

 heteroalbumose and dysalbumose. Such ap- 

 pearances can be observed in the case of prot- 

 albumose and dysalbumose only when extraor- 

 dinarily concentrated solutions, or solutions 

 rich in salt, are used. 



Meyer has recently separated from benzene 

 oils thiophen, a substance the composition of 

 which is represented by the formula C4H 4 S. 

 It presents a close analogy in general reactions 

 with benzene, and reacts with diketones to 

 form highly colored compounds. 



New Processes. Prof. H. W. Vogel reported 

 to the Physical Society in May on the final 

 practical results of the researches which he has 

 conducted for many years on the means of 

 photographing colored objects in their natural 

 shades. Sensitive plates are known to be af- 

 fected only by the more refrangible rays, while 

 the less refrangible rays remain inoperative. 

 Hence quite unnatural pictures are obtained of 

 colored objects, for in them blue, even in the 

 darkest shades, appears as white ; and yellow 

 and red as black. In view of the fact that the 

 sensitive collodion is affected only by such rays 

 as are absorbed by it, Prof. Vogel has been 

 for years occupied with the attempt to make 

 his plate sensitive to less refrangible rays by 

 alloying the silver coating with a substance 

 capable of absorbing those rays. The experi- 

 ment was successful so far as the natural colors 

 were concerned, and the plates prepared ac- 

 cording to the theory invariably produced an 

 effect in the solar spectrum wherever the ab- 

 sorption bands of the alloy were found; but it 

 was impossible to obtain like results with arti- 

 ficial colors. Many coloring substances which, 

 when blended with the collodion, beautifully 

 reproduced the yellow of the solar spectrum, 

 were ineffective against the artificial and faint- 

 er yellow of painters. Prof. Vogel continued 

 his attempts as new and brighter colors were 

 discovered, till he succeeded in obtaining in 

 cosine and its derivatives coloring substances 

 possessing hardly more than a broad absorption 

 band in the yellow, which, when mixed in due 

 proportion with the dry gelatine plates, gave 

 the yellow of the colored objects quite clear in 

 the photograph ; but the blue was still always 

 brighter. Finally, inserting a yellow glass 

 between the object and the camera, he secured 

 a partial absorption of the blue rays while the 

 yellow was left unimpaired, and obtained pho- 

 tographs in which the blue as well as the green 

 and yellow, and partly even the red parts of 

 the colored objects, presented the vivid effects 

 of the original. 



A modification of Dumas's method for the 

 quantitative estimation of nitrogen is suggested 

 by Mr. Stillingfleet Johnson. Taking a long 

 combustion-tube, he draws out one extremity 

 into the form of an S. Freshly reduced me- 

 tallic copper is packed into the front of the 

 tube; behind this is a layer of cupric oxide; 



and at the extreme back of the tube a porce- 

 lain boat is introduced, containing in the front 

 half the substance to be analyzed, while the 

 remainder is filled with fused and powdered 

 potassium chlorate. The air having been ex- 

 pelled from the cold apparatus by a stream of 

 carbonic dioxide, a low red heat is applied to 

 the whole of the front part of the tube, to with- 

 in an inch of the boat containing the substance, 

 while carbonic dioxide still continues to be 

 passed over. When complete expulsion of 

 nitrogen from the ignited copper oxide has 

 been insured, the receiving apparatus for the 

 substance under 'analysis is arranged, and the 

 heat is gradually extended the stream of car- 

 bonic dioxide still passing backward toward 

 the porcelain boat, care being taken not yet to 

 disturb the potassium chlorate. As soon as 

 the evolution of nitrogen from the destructive 

 distillation of the substance to be analyzed has 

 ceased, the heat is allowed to extend to the 

 potassium chlorate, when evolution of oxygen 

 gas ensues. The remainder of the analysis is 

 simple. 



M. S. Wroblewski has shown that a fall of 

 temperature of 186 0. can be obtained by 

 the expansion of liquid oxygen. In continu- 

 ing his work, he discovered that a hydrogen 

 thermometer of small size could not be de- 

 pended upon, and therefore adopted a thermo- 

 electrical apparatus, the inductions of which 

 were afterward compared with a large hydro- 

 gen thermometer. By this method of work- 

 ing at the low temperature of 200 0., the 

 r^vTTTnj- f a v lt- could be measured, corre- 

 sponding with a change of $ of a degree in tem- 

 perature. "With this apparatus the author has 

 been enabled to measure the boiling-point of 

 oxygen, of air, of nitrogen, and of carbonic 

 oxide under the ordinary pressure ; these gases 

 having been obtained as liquids by leading 

 them from a metallic receiver, where they are 

 already compressed to 100 atmospheres, into a 

 glass tube closed at one end and immersed in 

 liquid oxygen. On the expansion of the oxy- 

 gen, the compressed gas is liquefied. When 

 the expansion is accomplished, the connection 

 of the tube with the receiver is broken, and it 

 is brought to the atmospheric pressure; the 

 liquid gas boils at a temperature correspond- 

 ing to this pressure. M. Wroblewski obtains 

 the following results: 



Degrs. C. 



Oxygen, boiling-point 184 



Air, boiling-point -192-2 



Nitrogen, boiling-point -1^3-1 



Carbonic oxide, boiling-point 198 



On evaporating these gases in vacuo, a tem- 

 perature of 200 C. can be obtained. It re- 

 sults from the above that ordinary air prom- 

 ises to be the refrigerator of the future. It 

 does not have to be prepared, only compressed 

 to the point of liquefaction, and then applied. 



The ordinary process for the extraction of 

 sulphur at the mines in Sicily and Italy by 

 roasting in kilns, or calcaroni, is wasteful of 

 sulphur, and causes poisoning of the air by 



