22 INFLUENCE OF FOOD PRESERVATIVES ON HEALTH. 



each meal was determined, and the results obtained from the anatysis 

 of canned goods or of composite samples were calculated to the moist- 

 ure content of the food for that meal. 



Dried composite samples of bread and potatoes were ground and left 

 in an unstoppered bottle, with occasional mixing, for several days, 

 until they had absorbed the maximum amount of moisture from the 

 surrounding atmosphere, when they were termed "air dried." They 

 were then subjected to analysis. The samples of air-dried substances 

 were weighed for all determinations within as short a space of time as 

 possible, although the change of moisture content after the equilibrium 

 was once reached would naturally not be very sudden. 



Owing to the difficulty of making a mixture sufficiently uniform for 

 sampling, each sample of eggs and pudding was dried and ground 

 before analysis, the moisture content in the fresh sample being pre- 

 viously determined. In the case of meat, fish, and oysters the sub- 

 stance as taken from the table was passed several times through a 

 sausage grinder and subjected to complete analysis without drying. 

 In some cases the duplicate results on these last-named products were 

 not so close as could be desired, and a repetition of the analysis was 

 necessary. Owing to the fact, however, that drying would liberate 

 fat and thus lead to great annoyance and inaccuracy in the preparation 

 of the sample it was considered best to examine the samples of meat, 

 fish, and oysters without drying. 



In all cases when samples of food were weighed for the table a sam- 

 ple for analysis was placed in a jar closed with a screw cap, and then 

 coated with paraffin to prevent the loss of moisture. The samples 

 were then placed in a refrigerator and kept until the following morning, 

 when they were examined promptly. The breakfast samples, how- 

 ever, were examined immediately. The determinations made were 

 water, nitrogen, phosphoric acid, fat, and heat of combustion. 



DETERMINATION OP WATER. 



From 2 to 20 grams of the sample, according to its water content, 

 were placed in a flat-bottomed dish (lead bottle caps, varying in diame- 

 ter from 2i to 3i inches, were employed) and heated over night in a 

 water-jacketed drying oven, at the temperature of boiling water. 

 This was a longer time than was required in the majority of cases, but, 

 considering the large volume of work, it was found impracticable to 

 dry simply to constant weight, and the errors due to a longer drying 

 than was necessary were found to be inconsiderable. All substances 

 were dried in the manner and at the temperature stated above. The 

 fact that the results obtained with fruits were too high, owing to the 

 dehydration of invert sugar at the temperature of 100 C., was consid- 

 ered, but owing to the varying sugar content of samples of different 



