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VII r. On the Apparent Change in Weight during Chemical Reaction. 
By J. J. Manley, Hon. M.A. Oxon., Dauheny Curator, Magdalen College, Oxford. 
Communicated hy Prof. J. H. Poynting, F.R.S. 
Received May 29,—Read June 27, 1912, 
Contents. 
Page 
Introductory.227 
The balance.229 
Reacting substances.230 
The reaction vessels.230 
Manner of conducting weighings ..231 
Results of experiments— 
(a) Series I.■. 234: 
(h) Series II.235 
Some possible errors.235 
The irregularities produced by air streams.236 
Errors arising from diS'erences in the areas of two vessels.238 
Weight of water skin on Jena glass.240 
Methods for removing water skins.242 
Variations in apparent weight due to temperature changes.245 
Final experiments with silver nitrate and ferrous sulphate.248 
Results of experiments— 
(c) Series III. 251, 254 
(J) Series IV. 252, 254 
Effects produced by heat and light upon the mixed reacting substances. 255-258 
Of a final experiment conducted with barium chloride and sodium sulphate.258 
(l) Introductory .-— During the year 1890 the late Prof. Landolt inaugurated his 
prolonged researches upon the apparent alteration in the total mass of chemically 
reacting substances. From the time of its inception until it was brought to a 
conclusion in 1907, the experimental work was freely varied both as regards the 
conditions and the nature of the chemical reactions involved. The methods and 
precautions adopted, together with the final results obtained, are to be found 
embodied and set forth in detail in Landolt’s important memoir, “ Uber die 
Erhaltung der Masse bei Chemischen Umsetzungen.”* 
* ‘ Konigl. Akademie der Wissenschaften,’ Berlin, 1910. 
2 G 2 Published separately, September 12, 1912. 
VOL. CCXII.-A 491. 
