

4 
a 
WEIGHT VARIATION OF PACKAGE FOODS. 3 
In 68 per cent of all the instances observed, the scales were used 
at 20 per cent or more of their capacity. For packages of below 25 
pounds such a capacity is quite adaptable and commercially avail- 
able, but for those of larger size a 400- to 600-pound scale is much 
more suitable to the packer’s general needs and more available on 
the market. Practicability and prevalence of the practices favor 
the selection of 20 per cent of the capacity on smaller sizes and 10 
per cent for the larger sizes as the minimum weight which may be 
weighed on scales to represent good commercial practice. Tare 
weights are usually made on the same scale as the gross weights. 
Adoption of tolerances on scales by the Bureau of Standards and 
the Annual Conferences of Weights and Measures Officials t favors 
the selection of these tolerances as a control on the condition of 
scales to represent good commercial practice. _ 
Inability to determine an exact balance and to set the poise 
exactly on a graduation are the principal errors in manipulating 
scales. In a supplemental experiment an inspector and two com- 
mercial packers weighed the same 50 packages under commercial 
conditions on a scale having a known sensibility reciprocal (weight 
required to move scale beam from exact balance to the limit of its 
motion). Only 9 of the 150 weights were in error by more than one- 
fifth of the sensibility reciprocal. The error in the manipulation of a 
scale in good condition is limited to the total sensibility reciprocal. 
No apparent hardship, therefore, would be exacted of the packer if 
one-half of the sensibility reciprocal were selected to represent good 
commercial practice as to this manipulation. 
Since the poise is commonly set with greater care than is used in 
estimating the equilibrium, and since the operation is very simple 
(setting a point on the poise to meet a line on the beam), no apparent 
hardship would be exacted of the packer if one-fourth of a minimum 
graduation were selected as the limit of error to represent good com- 
mercial practice in this manipulation. 
Accordingly, the following specifications have been selected to 
represent good commercial practice in packaging granular free- 
flowing products, such as tea, coffee, spices, etc.: 
1. That packages of 5 pounds and below be weighed net; larger packages may be 
weighed gross and tare. 
2. That the following types of scales be used— 
For packages of 5 pounds and below: Even arm balance, 1-pound beam, one- 
fourth ounce graduation. 
For packages of over 5 and under 25 pounds: Even arm balance, 2-pound beam, 
one-fourth ounce graduation. . 
For packages of 25 pounds and over: Platform scale, 50-pound beam, one- 
fourth pound graduation. 

1U.8. Dept. Commerce, Bur. Standards Circ. 61. 
