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Line 1 Line 2

1 test control y

= (y

-x

)/2

2 control test x

3 test control y

= (y

-x

)/2

4 control test x

5 test control y

= (y

-x

)/2

6 control test x

Confidence interval for the "test-control" comparison

The following equation is used to calculate a confidence interval for

the mean difference between test and control results in either of the

two designs described above. The equation is formally equivalent to

the paired t test in Section 12.1. The effective sample size "n", is the

number of switchovers or crossovers per line to the test reagent.

(n=3 in both the examples above).

1 ∑ (d

– d)

d ± ts

√

, where s

√

,n = number of test periods

n n – 1

12.2.3 The REFDIST approach to planning and

analysis of sequential plant trials

If performance data are available from a period of routine operation

under the control regime for some length of time before the trial

was conducted, they can be used to calculate statistical criteria for

planning and for judging the outcome of the trial.

The REFDIST (for "reference distribution") approach to analyzing

accumulated data on plant operations was pioneered by Cytec. It

provides a basis not only for calculating an objective criterion for

trial success, but also for identifying a trial design that is most pow-

erful for substantiating treatment effects in the presence of routine

variation. It takes correct account of the fact that, in continuous oper-

ations, data take the form of a "time series" of values that often fail

to conform to the assumptions required for simpler statistical analyses.

The basic idea of the approach is to calculate "test-minus-control"

differences in sets of consecutive measurements drawn from the

accumulated data, where the labels "test" and "control" are assigned

to the measurements in the same pattern as test and control condi-

tions would be implemented in the actual trial. Assuming that no

deliberate changes in operating conditions were being made when

these measurements were taken, the calculated differences reflect

Statistical methods in mineral processing

259

routine variation, expressed in a form that is directly comparable to

the actual trial result. If significant changes to plant operating condi-

tions were made during the "base-line" period, it may be possible to

modify the REFDIST analysis to take these into account.

The set of calculated differences, or reference distribution, can

validly be used to assess the outcome of the actual trial. When the

difference observed in the actual trial exceeds in magnitude most

or all of the differences tabulated in the reference distribution, the

conclusion may reasonably be drawn that the change in operating

conditions has a real effect on the performance of the process. This

use of the reference distribution for trial evaluation is an alternative

to the Student’s t confidence interval. The reference distribution is

also valuable for planning purposes. A percentile of the reference

distribution for a given trial design measures the size of difference

between test and control reagents required to be reliably detected

with the proposed trial.

These criteria will be valid regardless of whether or not the varia-

tion conforms to the assumptions of standard statistical tests. In

particular, the assumption that each data point represents an inde-

pendent random sample of process performance is often violated in

the plant trial situation. Their validity does depend, however, on the

amount and form of the routine variation that occurred when the

data were accumulated being representative of the routine

variation that occurs during the actual trial.

An example using plant data to plan a trial

The following figure illustrates copper grade recorded for each

12-hour shift over a three-month period. The data were extracted

from the plant database to help in planning a trial to compare a new

collector to the standard (control) collector.

The REFDIST approach can be used with these data to calculate

"critical values" that a Test-minus-Control difference in average

grade recorded in the trial must exceed in order to "stand out" from

Mining Chemicals Handbook

260

20 40 60 80 100 120 140 160 180 200

Shift Number

ade % Cu

the routine variation. The calculations can be done for each of

several possible trial designs and the results compared to see which

design gives the smallest critical values.

The following figure illustrates the reference distribution for one

particular trial design, a single switchover design comparing average

grade during 22 consecutive shifts of operation with the test collector

with average grade during the preceding 22 consecutive shifts of

operation with the control collector. The conclusion of the REFDIST

analysis is that the Test-minus-Control difference in average grade

must be at least about 5.2% before it is larger than most (95%) of the

values in the reference distribution.

If instead of a single-switchover design a multiple-switchover design

is used, the Test-minus-Control difference needed to stand out from

routine variation will generally be smaller. The following figure illus-

trates the reference distribution for an alternative trial design of the

same length (44 shifts) where switching from test to control or vice

versa is done every shift. For this design, the Test-minus-Control dif-

ference in average grade need be only about 1.2% before it is larger

than most (95%) of the values in the reference distribution.

For more information about the Cytec REFDIST P/C software pro-

gram and how to use it, please consult your local Cytec representative.

Statistical methods in mineral processing

261

-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7

Avg T - Avg T - Avg C diffvg C difference Total number otal number of differences = 140

Frequency

equency

-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7

Avg T - Avg C diffvg C difference Total number otal number of differences = 140

Frequency

References

1. G. E. P. Box, W. G. Hunter, and J. S. Hunter, Statistics for

Experimenters, Wiley, New York, 1978. A classic textbook covering

the logic of comparative statistical tests, factorial experimental designs,

and statistical model building.

2. D. C. Montgomery, Design and Analysis of Experiments, 4th

ed., Wiley, New York, 1997. A thorough text aimed at engineers, with

a conventional approach to the subject matter.

3. J. A. Cornell, Experiments with Mixtures, 2nd ed., Wiley-

Interscience, New York, 1990. Detailed exposition of mixture designs

and their analysis.

4. Stat-Ease, Inc., Design-Expert, Minneapolis MN, 1999.

Specialized software for designing and analyzing response surface and

mixture experiments.

5. M. F. Triola, Elementary Statistics, 4th ed., Benjamin Cummings,

Redwood City CA, 1989.

6. P. J. Brockwell and R. A. Davis, Introduction to Time Series and

Forecasting, Springer-Verlag, New York, 1996.

7. R. Caulcutt, Data Analysis in the Chemical Industry, Volume 1:

Basic Techniques, Wiley, New York, 1989.

8. G. Box and A. Luceno, Statistical Control by Monitoring and

Feedback Adjustment, Wiley, New York, 1997.

9. M. R. Middleton, Data Analysis Using Microsoft Excel, Duxbury

Press, New York, 1997.

10. E. L. Grant and R. S. Leavenworth, Statistical Quality Control,

6th ed., McGraw-Hill, New York, 1988.

11. T. P. Ryan, Statistical Methods for Quality Improvement, Wiley,

New York, 1989.

12. Meyer D. and Napier-Munn T. (1999) Optimal experiments for

time dependent mineral processes. Australian and New

Zealand Journal of Statistics, 3-17.

13. Napier-Munn T. J. and Meyer D. H. (1999) A modified paired

t-test for the analysis of plant trials with data auto-correlated in

time, Minerals Engineering, Vol. 12, No. 9, 1093-1109.

Mining Chemicals Handbook

262

.13

SAFE HANDLING, STORAGE

AND USE OF

CYTEC REAGENTS

Mining Chemicals Handbook

264

Section 13 Safe handling, storage, and use of

Cytec’s reagents

Introduction

Cytec has established a reputation as a safety and environmentally

conscious manufacturer of mining chemicals. The number one

priority is that our customers have and use all the information

provided in this section regarding the recommended safe

procedures for handling, storage and feeding of Cytec’s products.

In this section you will find information on the following:

1. Material Safety Data Sheets (MSDS)

– where to obtain a copy

– how to read and interpret.

2. Contact information for your local Cytec representative.

3. Cytec’s safety consultants.

4. Materials of Construction for safe handling, storage and use of

Cytec’s reagents.

5. Emergency Response and Incident Management (ERIM) Policy.

6. Product Stewardship.

7. Safety Aspects of Product Packaging and Delivery.

8. Handling and use of experimental products (TSCA statement).

Section 13.1 Material safety data sheets

The objective of the MSDS is to concisely inform you about the

hazards of the materials you work with, so that you can protect

yourself and respond to emergency situations. The purpose of an

MSDS is to tell you:

• The material’s physical properties and health effects that may

make it hazardous to handle.

• The type of protective clothing you need.

• The first-aid treatment to be provided when you are exposed to a

hazard.

• The pre-planning needed for safely handling spills, fires, and

day-to-day operations.

• How to respond to accidents.

• How to safely store the product.

Safe handling, storage and use of Cytec reagents

265

Cytec provides an MSDS for all of its products. You may obtain an

updated copy by contacting your local representative, Cytec office,

or by accessing the Cytec website at www.cytec.com on the Internet.

For an explanation of what an MSDS can tell you about a material

you may obtain a copy of "The MSDS Pocket Dictionary" from

Genium Publishing Corporation , One Genium Plaza, Schenectady,

NY 12304-4690 – tel: 518-377-8854 / e-mail: sales@genium.com

Section 13.2 Contact information

Please refer to the end of the Handbook for locations of Cytec

offices worldwide.

Section 13.3 Cytec safety consultants

Cytec has experts in the safety aspects of our chemicals and they are

available for consultation. Contact your local representative or a

Cytec office.

Section 13.4 Materials of construction compatibility

Most of Cytec’s products are compatible with stainless steel, mild

steel, cast iron, high-density polyethylene, high-density polypropy-

lene, PT FE materials and phenolic or epoxy thermosetting materials.

Do not use copper, brass, aluminum, rubber, PVC or Tygon tubing

in feed or storage system. For more details of a specific product,

consult the product data sheet.

Section 13.5 Emergency response & incident

management (ERIM) policy

We at Cytec are committed to protecting the public safety and envi-

ronment. In the event our products or materials are involved in an

incident, a timely and effective response will be made.

Our objectives are:

• First, and foremost, to help protect the public safety and environ-

ment by prevention of transportation incidents.

• To provide an appropriate response in the event of an incident

involving one of our products or materials.

• To comply with all appropriate government regulations.

• To work to improve the safe practices and procedures of shippers,

transporters, and receivers as they relate to the handling of Cytec’s

products and materials

Mining Chemicals Handbook

266

• To address public concerns about chemical transportation hazards

by continuing education programs and communication with the

public and designated public emergency response agencies.

For an updated brochure please contact your local representative

or a Cytec office and refer to brochure # CGL-146

Section 13.6 Product stewardship

Cytec Industries is concerned about the health and well being of

our customers, employees, and the community. Cytec is committed

to reviewing and improving upon its manufacturing processes and

products to minimize any adverse safety, health and environmental

impacts. In accordance with this commitment, Cytec will strive to:

• Design safe, energy-efficient, and environmentally sound products

and processes.

• Transport products safely in packaging which conserves resources

and meets customers' needs.

• Bring value to its customers and shareholders by continually

improving its products and processes.

• Enhance partnerships with its customers, suppliers, and the com-

munity to fulfill these responsibilities.

Product Stewardship is the responsible and ethical management of

the health, safety and environmental aspects of a product from its

inception through production to its ultimate use and disposition.

Product Stewardship is part of the Responsible Care

Initiative of

the American Chemistry Council (ACC) of which Cytec is a charter

member. For our brochure on PRODUCT STEWARDSHIP, please

contact your local representative or a Cytec office and request

brochure # CGL-188.

Section 13.7 Safety aspects of product packaging

and delivery

Products from Cytec are available in steel or plastic drums, totes,

and in bulk tank trucks or tank cars. Contact your local Cytec repre-

sentative or a Cytec office on advice for a suitable package for your

application.

Safe handling, storage and use of Cytec reagents

267

Section 13.8 Safe handling of research samples

Cytec is constantly investigating and developing new products for

the mining industry. Such materials are available free of charge in

50ml to 1L quantities for investigative purposes only. Since these

products are at various stages of development, and are not commer-

cially available, MSDSs may or may not exist.

Cytec's policy is to provide to the researcher or testing lab request-

ing such a sample, sufficient information to handle, use, and store

the material safely. Typically, literature will accompany the sample

indicating pertinent hazard information about the product such as

flammability, skin contact, and the correct storage conditions, along

with other helpful physical properties. At various times, an MSDS of

a commercial product similar to the experimental sample will be

sent, delineating the most likely hazard and storage information. In

either case, all research samples will be labeled as shown below to

indicate they are for investigative use only and must be handled

safely by technically qualified personnel.

RESEARCH SAMPLE – FOR INVESTIGATIONAL USE ONLY

Important! The chemical and toxicological properties of this

material have not been fully investigated. Its handling or use may

be hazardous. Exercise due care. Since this material may contain

chemicals not included in the Toxic Substance Control Act Inventory,

it must be used under the supervision of technically qualified indi-

viduals. Materials not included in the Toxic Substances Control Act

must not be used for commercial purposes.

Please contact your local Cytec representative for sample requests.

References

1. Bretherick, L, 1999. Bretherick's Handbook of Reactive Chemical

Hazards: An Indexed Guide to Published Data, 6th. ed.,

Butterworth-Heineman, Oxford; Boston

2. Lewis, R. J. Sr., 2000. Sax's Dangerous Properties of Industrial

Materials, 10th. ed., Wiley, New York.

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