November 14, 1913] 



SCIENCE 



715 



paeity of the film to X-rays is negligibly small. 



A series of exposures of three kinds of plates 

 (Seed 23, 30 and X-ray) to light and X-rays have 

 been made to determine this point. In all the 

 fifteen exposures to X-rays the curves showing den- 

 sity against log exposure were practically similar 

 to the curves obtained by light exposure. The 

 equation 



J> = 7 (log E — log i) 

 was found to fit the straight part of the curves as 

 well as for light curves. 

 A. S. McDaniel: The Theory of the Acid Fixing 



Bath. 



The amount and nature of free acid which can 

 be added to a thiosulphate fixing bath is shown to 

 be dependent upon the equilibrium conditions of 

 either or both of the following reversible reactions, 

 one of which takes place between ionized, the 

 other between undissociated molecules : 



(1) S„"0^ _f- H . <:± HSO; + S, 



(2) Na^S^Os + 2HX ?^ 2NaX + N^SOj + S. 

 According to equation (1) the absolute concen- 

 tration of the hydrogen ions can be increased only 

 by increasing the concentration of the HSO3 ions 

 at the same rate. Similarly, according to equa- 

 tion (2) the absolute concentration of acid can be 

 increased only by keeping the ratio of the con- 

 centration of H^SO to HX above a certain definite 

 limit, depending upon the solubility of sulphur. 



In practise these conditions are fulfilled by add- 

 ing sulphurous acid or a mixture acid or a mixture 

 of sulphite and acid to the bath. 

 WiLDEK D. BANCEorT: The Latent Image. 

 Wilder D. Bancroft: Theory of Developer. 

 G. B. Frankforter and W. Kritchevsky: The 

 Action of Chloral and Bromal on the Polycyclic 

 Hydrocarbons in the Presence of Aluminium 

 Chloride. 

 G. B. Frankforter and E. B. Daniels: The Ac- 

 tion of Aluminium Chloride on Aliphatic Hthers. 



DIVISION OF FERTILIZER CHEMISTRY 



Paul Eudnick, Chairman 

 J. E. Breckenbridge, Secretary 



Paul Rudnick: Chairman's Address. Fertilizer 

 Chemistry. A Beport of Progress. 



L. A. Watt and W. T. Latshaw: On the Use of 

 Alundum Cruciiles in the Determination of 

 Phosphoric Acid. 



H. W. Hill and W. S. Landis: The Analysis of 

 Complete Fertilizers Containing Cyanamid. 



Paul Rudnick and W. L. Latshaw: On the Prep- 

 aration of Neutral Ammonium Citrate Solution. 



section OP INDIA RUBBER CHEMISTRY 



D. A. Cutler, Chairman 



Dorris Whipple, Secretary 



D. A. Cutler: Chairman's Address. Crude Bub- 



ber. 

 G. H. Savage: Some Befinements of the Ignition 

 Method for the Determination of Bubber in Vul- 

 canized Goods. 



WATER SEWAGE AND SANITATION SECTION 



Edward Bartow, Chairman 

 Harry P. Corson, Secretary 

 Edward Bartow and H. P. Corson: Manganese 

 in Illinois Waters. 



The city supplies of IMt. Vernon and Peoria, 111., 

 contain manganese which has caused serious in- 

 crustation in pipes. The Mt. Vernon supply con- 

 tains .5 part per million of the element while the 

 wells of the Peoria supply contain from .02 to 1.2 

 parts per million of the element. Samples of in- 

 crustation examined contain as high as 38 per cent, 

 of manganese. 



Edward Bartow and Clarence School: A Com- 

 parison of a Calcium Lime with a Calcium-Mag- 

 nesium Lime for Water Softening. 

 Experiments show that during the various stages 

 of water softening there is a difference in the ac- 

 tion of a calcium lime and a magnesium-calcium 

 lime. Complete softening depends upon the amount 

 of available calcium oxide which the Ume contains. 

 Edward Bartow and Clarence School: The 

 Order of Beactions during the Softening of 

 Water with Lime. 

 Charles Baskerville: Ventilation of the Schools 



of New Tork City. (Illustrated.) 

 Frank E. Hale and W. Melia: Winlder's Method 

 for the Determination of Oxygen in Water ; the 

 Effect of Nitrite and its Prevention. 

 H. W. Eedfield and C. Huckle: A Comparative 

 Study of Methods for Determining Sulphur in 

 Peptone. 



Various methods for determining the total sul- 

 phur in peptone and for determining a part of the 

 sulphur only have been compared. 



For total sulphur the Liebig-Koch method has 

 been found to give the most accurate and most 

 consistent results in peptone; while for determin- 

 ing the easily oxidized part of the sulphur, diges- 

 tion with a saturated solution of potassium 

 chlorate in nitric acid has proved most valuable. 

 H. W. Eedfield and C. Huckle: The Determina- 

 tion of Sulphur in Certain Culture Media. 

 A study has been made of the amount of total 



