COLLECTION OF SAMPLES 2/3 
Collection of Samples. The collection of the sample of water is an 
important part of the analysis. If done carelessly, it may determine 
the results, which are secured in the later analysis. For chemical 
analysis, the samples should be collected in glass-stoppered bottles 
which are scrupulously clean. The stoppers should fit tightly and be 
protected during transportation by tying a piece of cloth over them. 
For bacteriological analysis, four-, six- or eight-ounce glass-stoppered 
bottles should be used. They should be cleaned as outlined before 
(Chapter I) and sterilized. After cooling and before shipment, the 
top of each bottle should be protected by a piece of cloth or tin foil. 
Specimens for bacteriological analysis should always be packed in ice 
during transportation. 
Interval before Analysis. ‘The analysis should be started as soon 
as possible after collection of the sample. The composition of water 
undoubtedly changes and for this reason certain examinations may be 
conducted in the field. Any time which may be allowed to elapse be- 
tween collection and analysis of samples is entirely arbitrary. The 
committee on “ Standard Methods” suggests the following as being 
fairly reasonable maximum limits. 
Physical and Chemical Analysis. 
Ground Waters.... 0.0... c ccc cece eee e eens 72 hours 
Fairly pure surface waters........... 0.2.22 e ee eeeee 48 hours 
Polluted surface water... 00... 0... cece cece eee ene 12 hours 
Sewage effluents........ 0... 02 cece eee eee eee eee ee 6 hours 
Raw SCWAZC. 2... cece ee crete eee eens 6 hours 
Microscopical Examination. 
Ground waters... 0.0.0... cc ccc cece ete cece enna ees 72 hours 
Fairly pure surface waters.............. 2.0 c eee eee 24 hours 
Waters containing fragile organisms................. Immediate 
examination. 
Bacteriological Examination. 
Samples kept at less than 10°C........ ....-...205. 24 hours 
The directions for collecting samples of water are summed up in the 
following pages which are used by the Illinois State Water Survey. 
