SCIENTIFIC SUMMARY. 
199 
CHEMISTRY. 
A Neiu Process for Organic Analysis has been described by Herr M. F. 
Schultze, and is founded on the analysis of the g-aseous products. Herr 
Schultze burns the substance to be analysed with chlorate of potash in a tube, 
previously exhausted and sealed, and he states that its advantage is the small 
amount of material necessary for the operation. The following is the new 
mode. Herr Schultze first introduces the mixture, together with rather 
more than enough chlorate for complete combustion, into a combustion 
tube, sealing it at one end, and drawing it out at the other ; after having 
exhausted and measured the pressure of the remaining air, he seals the tube, 
shuts it up in a gun barrel, and heats it to a dull red heat for twenty 
minutes. When cold, he breaks the point of the tube under mercury, and 
collects the gas in a eudiometer. By measuring the quantity of carbonic 
acid formed, and absorbing it by potash, are to be found all the elements 
necessary for the calculation of the composition of an organic matter con- 
taining only carbon, hydrogen, and oxygen. If the carbon absorbs its proper 
amount of oxygen, and the compound is a body corresponding to a hydrate 
of carbon, such as starch, the gaseous material obtained is exactly equal to 
the amount of oxygen supplied by the chlorate of potash used. If more gas 
be found, it is because the body contains more oxygen than is needed to 
burn all its hydrogen ; if, on the contrary, there is less gas, it is because the 
body contained an excess of hydrogen with respect to its oxygen in the 
constitution of water. Vide Zeitschrift fur Anal. Chem. t. v. p. 239 j and new 
series, t. iii. p. 391. 
Action of Ozone on Sensitive Photographic Plates. — In a paper read before 
the Dublin Chemical Club (Dec. 12), Dr. Emerson Reynolds stated that he 
had been performing some experiments upon the above subject, and that he 
had found that when the latent image (i.e. the image before it is developed) 
was submitted to the action of ozone, it was completely obliterated — not only 
was it impossible to develop the image, but a second image might be re- 
taken in the camera upon the same plate. The author remarked that this 
was against the theory which might be called the mechanical theory of 
photographic images. 
Svnple Test for Alkaline Carbonates in Water. — A simple test of the pre- 
sence of these salts in spring or river water has been described by a writer 
(J. W. Y.) in the Chemical News. This test is as follows, and would con- 
stitute an excellent lecture experiment. It is dependent on a logwood re- 
action. The experiment may conveniently be performed by adding an equal 
quantity of the logwood solution to the water or waters to be tested, con- 
tained in glass jars or beakers, placed on white paper, a similar jar of dis- 
tilled water being used for comparison. The solubility of carbonate of lime 
in pure water may be shown by placing some pulverised calc-spar on a 
properly purified filter, and allowing distilled water to pass through it ; on 
adding a few drops of the logwood solution to the filtrate, a deep purplish 
red colour is immediately produced. An alcoholic solution of alizarine may 
be used instead of the logwood decoction ; with distilled water a yellowish 
colour is produced, but if any alkali or alkaline earth be present, a violet 
