216 Scientific Intelligence. 



ously weakened before reaching the collodion. If, however, the 

 prepared plate be exposed to the spectrum from the back side, this 

 difficulty will be avoided. Moreover, in this way the action of im- 

 perfectly transparent coloring matters may be tested.— ^er. Berl. 

 Chem. Ges., viii, 1635, Jan., 18Y6. g. f. b. 



3. Corrosion of FiaHnwn mils by Sulphuric Acid.— In 1862, 

 Schfxteer-Kestner communicated to Dr. Hofmann the results 

 obtained by him in concentrating sulphuric acid in stills of plati- 

 num, which were published by the latter in his Report. The 

 figures there given having been criticised as exaggerated,^ the 

 author now publishes further facts upon this question. From 

 1851 to 1861, 4309 tons of sulphuric acid were concentrated to 

 ■ alembic, the body of which weighed 40 kilograms. 



The entire loss of this part of the still was 12295 : 

 grams for each ton of acid. To destroy the nitrous product 

 vhich were the cause of this large loss, ammonium sulphate wa 



added in amount just sufficient for the purpose. In 1862, 1843 

 tons of acid were concentrated in the still, with a loss of 2490 

 grams; being 1*22 grams of platinum for each ton of acid, a 

 marked decrease. From 1864 to 1875, 1Y516 tons of acid (of 

 1000 kilograms each) were concentrated to 66° in a still the body 

 of which weighed 50 kilograms. The acid contained no nitrous 

 compounds, and only sulphurous acid. The loss of the still was 

 16178 grams, or 0-925 grams to the ton of acid. To produce 

 acid therefore of 66° B. containing 94 per cent HgSO^, there is a 

 loss to the still per ton of acid of one gram when nitrous com- 

 pounds are absent, and of 2^ to 3 grams when they are present. 

 These numbers are much increased however, by carrying the con- 

 centration above 66°. In a still weighing 30 kilograms^ 180 tons 

 of acid were produced, containing 97-98 per cent real acid. The 

 still lost 1092 grams platinum, or 6-07 grams per ton of acid. In 

 producing 47 tons of acid of 99| per cent, there was a loss of 8*80 

 grams platinum per ton of acid. An analysis of the acid itself 

 showed 8-38 grams of platinum to the ton, in solution in it. To 

 the figures here given for the loss of the body of the retort, about 

 13 per cent should be added for the other parts. It appears then 

 that this loss of platinum in concentrating sulphuric acid is actual, 

 and that it is a chemical not a mechanical one. The use of a 

 platinum-iridium alloy for the stills prevents to a large extent this 

 action, but the brittleness and consequent fragility of the alloy is 

 - • ' " '• • '^ " ■ "' Dec, 



4. Production of a Secondary Hexyl ^Zco^o^.— Oechsner de 

 CoNixcK has studied the products obtained by the hydrogenation 

 of ethyl-butyryl, a mixed acetone discovered by M. Friedel 

 among the products of the dry distillation of calcium butyrate. 

 To obtain the ketone, two kilograms of this salt were distilled in 

 """ ' 1 of distillate, which 



3onsiderable methyl- 

 butyral, 80 grams of a limpid highly refractive liquid of a strong 



