August 20, 1909] 



SCIENCE 



253 



should be clear. One takes 100 c.c. of the filtrate 

 and from a burette adds ji/10 NaOH until the 

 neutral point is reached. The presence of phos- 

 phates may tend to obscure somewhat the end- 

 point, but a little care enables one to get within 

 a drop of the neutral point. The percentage of 

 casein is calculated from the obtained results as 

 follows: Divide the number of cubic centimeters 

 of acid used by 2, subtract from this the number 

 of cubic centimeters of alkali used to neutralize 

 100 c.c. of filtrate and multiply the result by 

 1.096. By using 22 c.c. of milk, the difference 

 between one half of acid and of the alkali gives 

 percentage directly without multiplying by a fac- 

 tor. The method gives satisfactory results when 

 carried out with proper care. A determination 

 can be completed in twelve to fifteen minutes, a 

 half dozen or more can be made in about forty- 

 five minutes when all conveniences are at hand 

 and the manipulations are well under control. 

 The Determination of Nitrates in Potable Waters 

 with High Chloride Content: J. Peabce Mit- 

 chell. 



The conditions most favorable for the use of 

 the " phenol-sulphonic acid method " were found 

 to be: care in preventing evaporation of sample 

 to complete dryness in the water-bath, prompt 

 addition of the acid, use of an excess of acid 

 (1.5 c.c. at least), and allowance of time for the 

 completion of the reaction with the acid before 

 dilution. Standards prepared according to Ma- 

 son's suggestion gave the best results. With the 

 reduction method the Cu-M couple in the presence 

 of an excess of oxalic acid (0.5 g. per 100 c.c. of 

 sample) was used. Reduction was complete in 

 fourteen hours. The NH3 is best determined by 

 distillation, and nesslerization of the distillate. 

 In the case of very high nitrate content the dis- 

 tillate is better collected in a standard acid solu- 

 tion. From laboratory experiments with solutions 

 of known concentrations, and from the analysis 

 of fifty-one samples of natural water by both 

 methods, it appeared that the reduction method 

 gave the better results with low nitrate content. 

 The procedure recommended is to use the reduc- 

 tion method for routine work; if the nitrate con- 

 tent is found to exceed five parts per million to 

 repeat the determination, using the " phenol-sul- 

 phonic acid " method and, if the chlorides exceed 

 ten parts per million, standards prepared accord- 

 ing to Mason's suggestion. 



The Normal Chloride Content of the Surface 

 Waters on the San Francisco Peninsula: J. 

 Peabce Mitchell. 



From an area of 650 square miles 250 samples 

 were collected at diflerent seasons from 126 

 points. High chloride content, as compared with 

 eastern waters, and wide local variations were 

 found. Actual values varied from 9 to 50 parts 

 per million in unpolluted streams. Discussion of 

 the general climatic conditions, rainfall and ocean 

 winds as factors leading to high values. Consid- 

 eration of the topography, character of vegetation, 

 exposure to ocean winds and wide local variations 

 in rainfall (15-50 inches) as factors producing 

 great local variations in normal chloride values. 

 Emphasis of importance of study of local condi- 

 tions, determination of local standards, and need 

 of caution in interpretation of analysis from 

 regions not investigated. 



The Relation between the Calcium and the Fat 



Content of Cream: Hebmann C. Ltthgoe and 



Clarence E. Maksh. 



This work was undertaken with the view of 

 finding the maximum amount of calcium present 

 in cream beyond which adulteration could be de- 

 clared. The samples used were known purity 

 samples, the cows having been milked and the 

 cream separated in the presence of an inspector 

 or analyst of the Massachusetts State Board of 

 Health, samples separated from milk collected by 

 the inspectors, and commercial samples found 

 free from sugar by the Baier & Neumann reaction. 



The calcium was found to decrease as the fat 

 increased and the figures were plotted. From the 

 plot the following results were taken: 



The Determination of Benzoic Acid in Food Prod- 

 ucts: Edmund Clark. 



The method proposed for the determination of 

 benzoic acid consists in utilizing both ether and 

 chloroform as extractive agents as follows: An 

 aliquot portion of the filtrate, obtained by filter- 

 ing a weighed amount of the substance which has 

 been mixed with water and made up to a definite 

 volume, is acidified with HCl and shaken out with 



