Filter-Press Method of 

Extracting Water Samples 

For Chloride Analysis

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1544-A

Prepared in cooperation with 

the Nassau County Department oj 

Public ff^orks and the New York 

State fFater Resources Commission

Property o£

WATER .' .OURCEJ DIVISION 

GROUNi) V/ATER BRANCH
Filter-Press Method of 

Extracting Water Samples 

For Chloride Analysis

By NORBERT J. LUSCZYNSKI

GENERAL GROUND-WATER TECHNIQUES

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1544-A

Prepared in cooperation with 

the Nassau County Department of 

Public fj^orks and the New York 

State Heater Resources Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1961
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington 25, D.C.
CONTENTS

	Page 

Abstract- _ _____-___---_-______-__-_______-___-_---__-_-._--------- A-l

Introduction-_____--___--_____._____-__-___-_-__--__-_--___-___--_ A-l

Filter press.__-____-________________--_________-_____-___-_----_-- A-2

Filter-press method-_______________________________________________ A-3

Results at Atlantic Beach, Long Island, N.Y_____________--___-___---- A-5

Conclusions._ _-_________________--_____________-______-_----_-_--_ A-7

References________ _____________________-________-__-__-___--__---- A 8

ILLUSTRATION

Page 

FIGURE 1. Filter press and chamber assembly__ .____________---_-__--_ A-3

TABLE

Page 

TABLE 1. Chloride content of ground water at selected depths at Atlantic

Beach, Long Island, N.Y________________________________ A-5

in

603290 61

GENERAL GROUND-WATER TECHNIQUES

FILTER-PRESS METHOD OF EXTRACTING WATER 

SAMPLES FOR CHLORIDE ANALYSIS

By NORBERT J. LUSCZYNSKI

ABSTRACT

Determinations of chloride concentrations of ground water in fresh-water, 

diffused-water, and salt-water bodies were made after extracting water by the 

filter-press method during the drilling of a test well at Atlantic Beach, Long 

Island. N.Y., in 1959. The filter-press method is an adaptation of techniques 

used in the petroleum field.

The filter-press method was found to be suitable not only for sand and silt 

l»ut also for silty-clay and solid-clay core samples. It involves extracting 

interstitial water from core samples by means of a filter press and analyzing 

the filtrate for chloride content by titration. The method requires the identification and selection of the part of the core sample not invaded by the drilling 

mud during the coring operations. The invaded part* are identified by the 

distinctive green color of fluorescein dye added to the drilling mud. The results 

obtained by the filter-press method are consistent with those obtained by other 

methods.

INTRODUCTION

A detailed investigation of salt-water encroachment in southwestern 

Nassau County on Long Island, N.Y., was undertaken in 1958 by the 

U.S. Geological Survey in cooperation with the Nassau County Department of Public Works and the New York State Water Besources 

Commission. The investigation includes test drilling which is to 

provide basic data for the definition of the position of fresh-water, 

diffused-water, and salt-water bodies, and also for the definition of 

the salinities, densities, and hydraulic gradients of these bodies. A 

progress report on the first phase of the test-drilling program has 

been prepared (Lusczynski and Swarzenski, 1960).

The position and density of the fresh-water, diffused-water, and 

salt-water bodies are defined in part by the chloride content of the 

ground water brought up in core samples during the test drilling. 

Swarzenski (1959) described the centrifugal and dilution methods 

used during the first phase of the drilling program in 1958 to extract 

water from cores for determinations of chloride. The centrifugal

A-l
A-2 GENERAL GROUND-WATER TECHNIQUES

method was found to be suitable for accurate determinations of the 

chloride content of water in samples of sand, clayey sand, and silt. 

It involves, first, the extraction of water by means of a mechanical 

centrifuge, and then titration for chloride content. The dilution 

method was devised for solid and silty clays which yield little or no 

water by centrifugal extraction. The laboratory procedure for this 

method is rather complex. It requires (a) a determination of moisture content from the loss in weight of a selected part of a core when 

it is dried in an oven at a temperature of 180°F for about 24 hours, 

(b) the restitution of original moisture content and further dilution 

with distilled water, (c) re-solution of the salts precipitated during 

drying, (d) filtration, and finally (e) titration for chloride content. 

The dilution method in its present stage of development yields only 

approximate results.

During the second phase of the drilling program in 1959, a filterpress method was used; it produced reliable results under controlled 

conditions, not only with sand and silt but also with solid-clay and 

silty-clay samples. The results obtained by the filter-press, centrifugal, and dilution methods at a test well at Atlantic Beach, Long 

Island, N. Y., are described and compared in this paper.

The filter-press method was used previously by C. W. Lauman & 

Co., Inc., well-drilling contractors of Bethpage, Long Island, N.Y., 

for defining chloride concentrations in sand zones during the construction of a test hole for a supply well. However, the results obtained 

by the contractor were only approximate, principally because no precautions were taken to select material not invaded by the drilling fluid.

FILTER PRESS

The filter press used during the study (fig. 1) is one of several types 

sold commercially for use in determining filtration properties of drilling muds (National Lead Co., undated). It is used also in mud 

logging to obtain a rough measure of salinity of formation water.

The filter-press unit consists of a chamber, a filtering medium, a 

graduated tube for catching and measuring the filtrate, and a pressuresource unit. A cell, base cap, screen, rubber gaskets, and top cap make 

up the chamber. The cell is 3y2 inches high and has inside and 

outside diameters of 3 and Sy2 inches, respectively. The filtering 

medium is a sheet of filter paper which fits on the screen over the 

base cap; it has a filtering area of about 7 square inches. The filter 

paper used is specially hardened to withstand the pressure in the 

chamber. A graduated cylinder is used to catch the filtrate.

The chamber is partly filled with selected material, assembled, placed 

in the frame, and made airtight by the T-screw (fig. 1). Pressure
FILTER-PRESS METHOD OF EXTRACTING WATER SAMPLES A-3

"T" SCREW

PRESSURE INLET

SUPPORT ROD

GRADUATED CYLINDER

THUMB SCREW

SUPPORT

RUBBER GASKET

RUBBER GASKET 

FIUER PAPER 

SCREEN 

RUBBER GASKET

BASE CAP WITH 

FILTRATE TUBE

FILTRATE TUBE

FIGURE 1. Filter press and chamber assembly. Courtesy of Bariod Division, National

Lead Co.

introduced through an opening in the upper cap of the chamber forces 

interstitial water out of the material and into the filtrate tube through 

a small opening in the base cap.

The pressure device used at test wells on Long Island includes a 

container for a carbon dioxide cartridge, a pressure gage, and a regulator. Pressures of as much as 120 psi (pounds per square inch) can 

be attained with the carbon dioxide cartridges. Other pressure 

sources, such as compressed nitrogen and carbon dioxide in cylinders, 

which are sold commercially can be used.

The filter press illustrated is a low-pressure unit. A unit for 

pressures of as much as 900 psi is also available.

FILTER-PRESS METHOD

The filter-press method involves filtering interstitial wrater from 

the core sample by means of the filter press, and analyzing the filtrate 

for chloride content by titration with a standard silver nitrate solution. The analysis is usually completed in the field within minutes 

after the core sample is brought to the surface. The filter-press 

method is an adaptation of techniques in use in the petroleum field 

(National Lead Co., undated).
A-4 GENERAL GROUND-WATER TECHNIQUES

As with the centrifugal method, the requisites for accurate determination of chloride by the filter-press method are (a) use of uninvaded parts of the core sample, (b) minimum loss of formational 

water in the core sample during coring and during transferral of the 

selected part of the sample from the core barrel to the filter-press 

chamber, and (c) sufficient filtrate, consisting only of formational 

water, for analysis.

The samples are obtained in a split-spoon core barrel, 2 inches in 

diameter and 18 or 24 inches long. Partial invasion of the core 

samples is unavoidable with the use of present coring methods and 

techniques. Invasion occurs when the drilling fluid is forced by 

hydrostatic pressure into the formation at or near the sampling point 

before the core is taken; it occurs also when the drilling fluid finds 

its way into the core barrel during coring, and as the core is raised 

to the surface. Loose sand and gravel samples are invaded to the 

greatest degree, and solid clay to the least. The amount of invasion 

increases with time. Therefore, the time from the attainment of the 

desired depth and coring at the depth until the core is brought to the 

surface should be kept to a minimum.

Addition of fluorescein dye to the drilling fluid gives it a distinctive 

green color and permits visual detection of the invaded parts of the 

core sample. A fluoroscope can be used also to assure the selection 

of uninvaded material and to check the filtrate for the presence of 

even minute amounts of the drilling fluid. Other dyes, such as methyl 

blue, may be used for assuring a contrast between the color of drilling 

mud and that of the formation.

Uninvadecl parts consisting of loose material such as sand and 

gravel are transferred to the filter-press chamber by spatula or spoon. 

Usually it is not practical to remove much more than 25 to 50 percent 

of the uninvaded material from the core barrel by this method. 

Enough material is transferred to fill the chamber about a quarter to 

half full. It is then tamped lightly until an integrated unit is formed 

in the chamber and a film of water is formed on the surface of the 

material and along the cylindrical wall.

Usually less than 10 to 20 percent of a solid- or silty-clay sample is 

invaded by the drilling fluid. Plugs of the uninvaded material 1 to 2 

inches long are placed in the chamber to fill it about a quarter full. 

Then they are molded and tamped into an integrated unit. Difficulty can be experienced in molding and tamping a relatively dry 

solid clay one having a water content of less than 15 to 20 percent 

of the dry weight of the clay.

The total time between the opening of the split-spoon core barrel 

and the placing of the chamber in the frame is usually 1 to 2 minutes
FILTER-PRESS METHOD OF EXTRACTING WATER SAMPLES A-5

for the loose material and 2 to 5 minutes for the tight material. There 

is thus very little opportunity for evaporation.

After a sample is properly prepared for filtration, the chamber is 

fully assembled, placed in the frame, and made airtight by the T-screw 

(fig. \). The gas pressure is then applied.

The pressure of the carbon dioxide gas in the chamber moves some 

of the interstitial water through the filter screen and filter tube into 

the graduated cylinder. Pressures of 5 to 30 psi suffice for the gravel, 

sand, and silt samples. Pressures of about 100 psi are usually sufficient for silty- and solid-clay samples. The carbon dioxide gas does 

not alter the chloride concentration of water forced from the material 

into the filtrate tube.

Chloride determinations of the filtrate are made in the field by the 

standard titration method using silver nitrate solution (1 ml AgNO3 

1.0 mg Cl or 0.5 mg Cl). With these solutions, relatively large 

amounts of filtrate (25 to 50 ml) are needed when fresh water is to be 

tested, and relatively small amounts (1 to 10 ml) wThen salt water or 

diffused water is to be tested.

Usually enough filtrate can be obtained from the uncontaminated 

material of only one core if it is taken in a diffused-water or salt-water 

zone. However, more than one core may be necessary to obtain the 

required amount of filtrate if the core is taken in a fresh-water zone; 

this is particularly true for solid-clay samples, which yield only small 

amounts of interstitial water.

RESULTS AT ATLANTIC BEACH, LONG ISLAND, N.Y.

During the summer of 1959, an 850-foot test hole was drilled at 

Atlantic Beach, in the southern part of southwestern Nassau County, 

Long Island, N.Y. The hole penetrated unconsolidated material containing fresh water, diffused water, and salt water; core samples were 

taken at intervals of 5 to 20 feet. Chloride determinations were made 

by Swarzenski and the writer by means of the filter-press, centrifugal, 

and dilution methods. Determinations were made also of the chloride 

content of water pumped from three separate observation wells 

screened permanently at different depths in the test hole. (The hole 

was backfilled and relatively impermeable material was placed between 

the screens.) Results for sample tests for which more than one method 

was used, together with sample depths and descriptions, are listed 

in table 1.

Chloride concentrations determined by the filter-press method in the 

diffused-water zone at a depth of 150 feet and in the salt-water zone 

at a depth of 673 feet agree closely with those in related water samples 

from the individual wells screened at these depths. Chloride deter-
A-6 GENERAL GROUND-WATER TECHNIQUES

TABLE 1. Chloride content of ground water at selected depths at Atlantic Beach,

Long Island, N.Y.

Core 

sample

25

Death, 

in feet, 

below 

land 

surface

41

42 

52 

91 

101 

111 

150 

160 

170

170-171 

ISO-181 

260-261 

282-283 

291

311-312

346-347

384-385

386

445-446 

454

574

575

673

693-6<H 

733

733-734 

743-744 

763-764

764

773

774

Description

Silt__-_. -_._ ..... .-_ .......

,_...do ._.... ......... .....

._ .do .-.....-__.__.._..._.

... .do - .... . ..........

Solid clav. ... ---.- .-__.-.

Silt...... ... ... _______

Clay and silt . .

...do .... ... ... ...

Solid clav. .... . . ... 

Fine to medium clavev sand . _ 

_- -do . ......... .. __

Clay and silt. .._ -_ .

Fine to coarse gravel in clay

Very fine to medium clayey

.do -_ . _ . ......... .

Moisture 

content, 

in percent of 

drv 

weight

33

56 

41 

37 

35

22

24

18 

19

19

17

19 

23

Chloride content, in parts per million

Well 

sample

1 12, 900

213

316,000

Filterpress 

method

7,500

4PO 

1,600

2, 550 

12,900 

13, 100

1,600

50 

18 

21 

30 

62 

204

1. 8FO 

3,150

"15,000

15,400 

15,300

12,000 

10,800

11,100

10,900

4,400

Centrifii-ral 

method

13,500 

13,200

1,910 

3,200

14,800

10,700

Dilution 

method

9,000 

1,500 

430 

1,360 

2,280

" "5,000

1,2-10 

60

94

75

210 

1,570

"~"l4~000

10, 400

8,400 

7,200

1 Screen at 146-156 ft.

2 Screen at 284-294 ft. 

s Screen at 667-677 ft.

urinations by the filter-press method in the fresh-water zone at depths 

of 282-283 and 291 feet are several parts per million higher than those 

of water pumped from the well screened at 284-294 feet. The agreement of the results by the filter-press method at each of these two 

depths, as well as at the other depths in the zone of fresh or nearly 

fresh water between 260 and 347 feet, is only fair because only one core 

was taken at each of these depths, and as a result not nearly enough 

filtrate was obtained for a good determination of chloride.

The results for water extracted from sand and silt core samples by 

the filter-press and centrifugal methods are in close agreement. 

Less overall handling and preparation was required and more water 

per given volume of sample was obtained in a much shorter time by 

Ihe filter-press method than by the centrifugal method.

In the diffused-water and salt-water zones at Atlantic Beach, tests 

by the dilution method, in general, showed lower chloride content than 

those by the filter-press method. In the fresh-water zones, the tests 

by the dilution method showed higher chloride content than those by
FILTER-PRESS METHOD OF EXTRACTING WATER SAMPLES A-7

the filter-press method. Some small percentage of the difference in 

results by these two methods in the fresh-water, diffused-water, and 

salt-water zones may be due to actual differences in chloride content of 

water at points only a few inches to about a foot apart vertically at 

the site of the test hole. However, results from depths of 52, 91, 101, 

111, and 764 feet in diffused water in solid clay are comparable because 

adjacent sections of the core sample were purposely selected for the 

determinations by the filter-press and dilution methods. At these 

depths, the dilution method produced results averaging, for the five 

samples, about 12 percent lower than those obtained by the filter-press 

method. At the other depths in sand, silt, and clay zones, results may 

not be comparable, because adjacent sections of the core sample may 

not have been used for analysis by each of the two methods.

Chloride determinations were made by all three methods on one 

core sample, that at the depth of 445-446 feet. Results obtained by 

the filter-press, centrifugal, and dilution methods were 1,850, 1,910, 

and 1,570 ppm (parts per million), respectively. The material was 

fine to medium sand. For the filter press, material between 445 and 

446 feet was selected; for the centrifugal and dilution methods, material at 446 feet was used.

CONCLUSIONS

Experiments made during a program of test drilling for study of 

salt-water encroachment in southwestern Nassau County, Long Island, 

N.Y., indicated that accurate determinations of chloride concentrations of ground water in fresh-, diffused-, and salt-water bodies can 

be obtained from core samples by the filter-press method. This 

method can be used for sand, silt, and silty clay as well as solid clay. 

At the test well at Atlantic Beach, Long Island, N.Y., the results 

of chloride tests by the filter-press method, from gravel, sand, and 

silt samples, compare closely with those by the centrifugal method 

and those from analysis of water from finished wells. Results of 

chloride tests by the filter-press and dilution methods for fine sand, 

silt, and clay samples were generally in fair agreement.

The filter-press method is simple and direct. In this method, water 

is pressed out of the unmvaded part of a core sample and is analyzed 

for chloride content. The method is economical; basically it requires 

only a filter press, a chloride-testing kit, and a fluoroscope, all of 

which can be purchased for less than $200. It is rapid and convenient, in that each determination of chloride can be made in the field 

within minutes after the core is brought to the land surface.

Precautions must be taken to assure selection of material not invaded by the drilling fluid. These precautions include the use of
A-8 GENERAL GROUND-WATER TECHNIQUES

fluorescein dye and a fluoroscope to identify the invaded parts of 

the core samples, and the use of a fluoroscope to check the filtrate for 

presence of any minute amount of drilling fluid.

It is planned to continue experimentation with the filter-press 

method during the third phase of the test-drilling program on Long 

Island. Experimentation will be directed specifically toward improving coring techniques in order to reduce the amount of invasion 

in loose material. Further experiments will be made in techniques of 

preparing relatively dry clay samples in the filter-press chamber and 

of extracting more interstitial water from relatively dry clay samples 

under pressures substantially higher than 100 psi.

Efforts will also be made to improve the dilution method.

REFERENCES

Lusczynski, X. J., and Swarzenski, W. V., 1960, Position of the salt-water body 

in the Magothy(Y) formation in the Cedarhurst-Woodmere area of southwestern Nassau County, Long Island, N.Y.: Econ. Geology, v. 55, no. 8, 

p. 1739-1750.

National Lead Co., undated. Field testing of drilling muds: Houston, Tex., 

Baroid Div., 48 p.

Swarzenski, W. V., 1959, Determination of chloride in water from core samples: 

Am. Assoc. Petroleum Geologists Bull., v. 43, no. 8, p. 1995-1998.

U S. GOVERNMENT PRINTING OFFICE: 1961