In the preceding chapters considerable attention has been paid to the necessity for precision in all apparatus employed in sugar laboratory control work. However, accurate apparatus and refined methods of analysis are totally worthless if the material analysed is not representative of the total substance, the composition of which it is desired to determine. Sugar-mill products in particular present a most difficult problem in this regard, but unless complete and accurate methods of sampling are employed the labora- tory control must be regarded as only approximate and indefinite.
The method of sampling depends, of course, on the nature of the partic- ular product; and further, an accurate analytical result is of little value for control purposes if the total quantity of substance is not, in turn, accurately determined. Thus, a true analysis of a representative sample of mixed juice gives no measure of the quantity of sugar entering manufacture, unless the true quantity of such juice is also known. The necessity for the highest degree of precision in both sampling and measuring cannot be overemphasized. Yet all too often one finds that the supervision of these operations is placed in the hands of juniors, while the expert technician performs the analyses. It is certainly true that greater precision in results is often obtained by having the chief chemist carry out the sampling and by leaving the analyses to the laboratory junior, but it must be emphasized that, whoever takes the sample, it must be taken in a completely unbiased manner.
It must always be remembered that even the best sampling methods are approximate, and chemists should be continually on the watch for improve- ments in technique. The following methods are regarded by the Bureau as being simple and practicable, and at the same time, not unscientific. Cane
The correct sampling of a field of cane is quite a difficult matter. As the result of studies which have been carried out, it has been found that a large number of individual sticks must be selected at random from all parts of the field if an accurate estimate of its c.c.s. is desired. The number of stalks necessary depends on the degree of variation in crop growth from point to point in the block, particularly if the crop is far removed from maturity. From 20 to 50 sticks should be regarded as the range of sampling necessary. The best method for determining the degree of maturity of a crop is to carry through a series of systematic tests.
The collection of stick samples for fibre analysis was formerly a universal practice at Queensland mills. This method of cane sampling is fully described in Regulation 57 of the Regulation of Sugar Cane Prices Act, but it has been largely replaced by the practice of sampling prepared cane. Prepared cane samples can be used for the determination of cane fibre by disintegrating the sample in a hammermill or cutter grinder, transferring the sample to a fibre bag and determining fibre in the usual manner; or the prepared cane samples can be used for direct analysis of cane, utilizing the wet disintegrator to determine Brix and pol and a Spencer or similar type of air stream oven to determine moisture. Prepared cane is usually obtained from the elevator feeding into the number one mill hopper by means of a hydraulically or
SAMPLING OF SUGAR MILL PRODUCTS 79 p n e u m a t i c a l l y o p e r a t e d d o o r i n t h e b o t t o m o f t h e e l e v a t o r . I n o r d e r t o a v o i d
t h e risk o f i n c o r r e c t s a m p l i n g c a u s e d b y t h e p o s s i b i l i t y o f s e g r e g a t i o n i n t h e c a r r i e r , i t i s i m p o r t a n t t h a t t h e d o o r c o v e r a s m u c h o f t h e w i d t h o f t h e e l e v a t o r a s p o s s i b l e . T h e d o o r o p e n i n g s h o u l d also b e sufficiently w i d e t h a t a free fall o f t h e full d e p t h o f t h e c a n e i n t h e e l e v a t o r o c c u r s . T h e p r e p a r e d c a n e i s u s u a l l y a l l o w e d t o fall o n t o a l a r g e s a m p l i n g t a b l e w h e r e i t i s s p r e a d o u t a n d s u b - s a m p l e d b y h a n d for h a m m e r - m i l l i n g o r d i s i n t e g r a t i o n . V a r i o u s a v e n u e s for a u t o m a t i c m e c h a n i c a l s u b - s a m p l i n g a r e a t p r e s e n t b e i n g i n - v e s t i g a t e d .
Juice
Various devices are employed for obtaining continuous samples of juice from the mills and juice gutters. The simplest form is probably a metal container provided with a conical lid in which a small hole has been drilled. This hole is covered with fine gauze to exclude bagasse particles. The con- tainer is usually suspended in the stream of juice from the first roller of the train. Tests have shown that if three such vessels are suspended beneath the same roller the samples collected may vary in composition within relatively wide limits, and, therefore, it is essential to collect a sample from the full length of the roller.
This may be done by fitting a trough beneath the roller in such a way that the entire quantity of juice expressed by the roller is collected. At the centre of the trough a cup is provided to which is attached a large downpipe several inches long. The sampler is placed directly below the centre of the outlet.
This method suffers from a serious disability. The sample is collected at a uniform rate, irrespective of the rate of juice flow. With normal crushing the variation will not be great, and the sample obtained should be fairly representative of the entire juice; but this limitation should be borne in mind in those areas where the cane supply is frequently highly variable.
The size of the hole in the container determines the capacity of the sampler. If the hole is too large frequent changes are necessary, while if too small the sample is insufficient. For normal sampling the hole is made of such dimensions as to provide a gallon of sample juice every four hours.
For first expressed juice sampling this method has now been superseded by automatic continuous devices. Several types are in use in Queensland, but in all the collection of the sample involves the use of a trough to catch the juice, this trough being constructed to conform with Regulation 57 of the Regulation of Sugar Cane Prices Act. All of the juice flow from this trough is collected and fed into the suction of a juice sampling pump. By means of a proportioning device, part of the juice flow from the pump is diverted to a sample can system located adjacent to the first mill or in the laboratory, and the remainder returned to the mill bed. Normally the sample cans are held in an automatic sampling device which changes the sample flow from one can to the next as each successive rake of cane comes through the first mill. The samples are identified by means of pins or balls in sample wheels which have their speeds geared to the speed of the carrier or elevators, or, in the most recent type of automatic sampler, the samples are tracked through the conveying system electronically. This electronic sampler also has the facility of being able to alter the proportioning device so that a more or less constant quantity of juice is collected for each rake of cane, irrespective of the length of the rake.
Sampling from juice gutters also presents difficulties. The best device for this purpose is a small under-shot water wheel. One of the spokes is made
S O S A M P L I N G O F S U G A R M I L L P R O D U C T S
hollow and terminates in a spoon-shaped blade. This spoon takes up a little of the juice, which flows down the spoke to the hollow axle which is provided, and thence into the container. The main objection to this type is that the small pipes are liable to become choked, after which sampling will cease. In order to ensure a true average sample, small baffles should be fitted in the trough upstream from the wheel to effect a thorough mixing of the juice.
Sampling of mixed juice, particularly where suspended matter deter minations are to be carried out on the juice, is best accomplished by means of a pitot-tube type sampler placed in the delivery pipe from the mixed juice pump. In this way, a sample of the juice is taken before the suspended solids have had a chance to settle, and a reasonably accurate sample can be obtain- ed. A moving receiving tube which passes at regular intervals through the juice flowing from the sampling tube comprises an efficient method of sub- sampling the main sample flow.
Syrup
With the replacement of reciprocating syrup pumps by centrifugal pumps, samplers such as the Calumet described in earlier editions of this Manual are no longer applicable for the purpose of syrup sampling. Continu- ous sampling of syrup may be effectively carried out by piping a small sample of syrup from the pump delivery line and sub-sampling this smaller flow by means of a sample splitter. Syrup samplers must be checked and cleaned at regular intervals to ensure that crystallization does not occur, thus blocking the sampler. If continuous sampling is not used, syrup may be snap sampled at regular intervals and the snap samples composited over a period. Preserv- ative is not required for syrup, molasses, or massecuite samples. Massecuites and Molasses
The composition of massecuite varies from point to point within the pan, due to imperfect circulation, and therefore the sample should be taken continuously as the massecuite is discharging. For control purposes a "snap" sample is usually sufficient, though for preference three such samples should be taken and composited for each strike. These should be drawn at regular intervals as the massecuite is discharged, but the first should not be taken from the first flow of massecuite. In compositing samples of massecuite, care must be taken that the respective portions are proportional to the quantity of massecuite which each represents.
Molasses may be sampled similarly to syrup (q.v.) and similar precautions as with syrups should be taken in preparing a representative composite sample. It is preferable to obtain a continuous sample of final molasses. A convenient sampler for those mills using molasses scales is to fit a small pipe leading from the receiving tank to a sample container. Each time the weighing tank discharges, the inlet to this pipe is submerged to a similar depth, and the quantity of molasses transferred to the container is uniform.
Raw Sugar
Raw sugar is now handled in bulk in Queensland, and sugar sampling at the bulk terminals is carried out by removing a portion of the sugar from the bulk containers as they are being discharged. At the mill various devices are being used for sugar sampling. Theoretically, it is best to sample from a stream in free fall, and, if the practical difficulties could be overcome, this could be achieved on a sugar belt if the belt were fitted with a sampling gap, almost the full width of the belt, and a sample can placed under the belt at the feed point. This is however, a rather difficult and expensive method of
SAMPLING OF SUGAR MILL PRODUCTS 81 sampling and samples are usually obtained by means of motor-driven samp-
ling spoons or other devices. The disadvantages of these devices are that, unless very sophisticated control equipment is used, they are not strictly proportional to sugar rate and are easily fouled by wet sugar.
Bagasse
The accurate sampling of bagasse is a very difficult problem. Here, again, no satisfactory continuous sampler has been devised and hand sampling is necessary. In general the analyses of final bagasse samples are not considered individually, but only with reference to their average value, hence advantage may be taken of the fact that bagasse can be preserved for reasonable periods. In this way samples may be taken at frequent intervals without increasing the number of analyses to be made by the chemist.
For final bagasse the compositing of samples taken at short intervals, and the subsequent analysis of the well mixed sample, is strongly recom- mended in preference to the taking of "snap" samples once or twice per shift. The former method is far more representative of the bagasse in process, and the sampling procedure described below does not inflict any extra work on the analyst.
For sampling bagasse a small chute the width of the bagasse blanket is provided. This chute is held across and below the falling bagasse, and when it is full the contents are transferred to a closed container containing pre- servative. A suitable type is shown in Fig. 37. The chute should hold 2 or 3 lb of final bagasse so that the resulting
total sample is about 30-50 lb. When the composite is completed the large sample is spread out, rapidly but effectively mixed, and then sub-sampled for analysis. The mixing must be carried out thoroughly, otherwise the whole sampling process will have been wasted; but it must be done quickly to avoid moisture loss by evaporation. This loss is to a certain extent minimized by the fact that, by the time mixing is carried out, the temperature of the sample will have dropped to approximately that of its sur- roundings.
In mills where sudden changes in varieties and condi- tions occur, half an hour should be the maximum interval, whilst in others where conditions are comparatively uniform a one-hour period is permissible. The time schedule for sampling should be adhered to, irrespective of milling conditions, as long as the mill is
crushing. The composite sample Fig. 37—Illustrating container recommended is preserved by means of a pad for compositing samples of bagasse.
82 SAMPLING OF SUGAR MILL PRODUCTS s a t u r a t e d w i t h s t r o n g a m m o n i a a n d c h l o r o f o r m ( p r o p o r t i o n s 6 : 1 ) o r t o l u e n e . W h i l e , a s m e n t i o n e d p r e v i o u s l y , final b a g a s s e c a n b e p r e s e r v e d for a r e a s o n a b l e l e n g t h of t i m e , four h o u r l y a n a l y s i s p e r i o d s a r e c o n s i d e r e d p r e f e r a b l e t o a o n c e p e r shift a n a l y s i s o f t h e c o m p o s i t e . S a m p l e s f r o m e a r l i e r mills i n t h e t r a i n a r e u s u a l l y i n t e n d e d t o s u p p l y t h e e n g i n e e r w i t h specific i n f o r m a t i o n a n d m a y n o t b e i n t e n d e d for c o n t r o l p u r p o s e s . H o w e v e r , s o t h a t t h e s e s a m p l e s c a n b e r e l i a b l e , t h e y s h o u l d b e t a k e n o v e r a p e r i o d o f t i m e w i t h a s h o v e l . I t i s i m p o r t a n t t h a t t h e full d e p t h o f b a g a s s e b e s a m p l e d since t h e t o p s u r f a c e m a t e r i a l h a s a h i g h e r j u i c e c o n t e n t t h a n t h e r e m a i n d e r . Also s a m p l i n g s h o u l d b e c a r r i e d o u t a c r o s s t h e full w i d t h of t h e roller. Filter Cake
With the rotary filter, next to weighing at regular intervals the complete out-turn of cake in a given time, the following procedure is recommended. The length of the filter is divided into a suitable number of equal portions. At half hourly intervals the mud from one or more screen segments (depend- ing on the size of the screens and the length of the portion) is caught on a suitable tray. This quantity of mud from the known area of screen is then weighed, and a small area removed by means of a sampler resembling a scone cutter. The weight of mud in each trayful is recorded and the small samples composited in a closed container for subsequent analysis. At the end of a period the total weight of cake produced by the filter can be calculated from the following expression:—
where W = total weight of cake for the period, in tons
w = average weight contained on mud sample tray in pounds n — revolutions of filter during period (preferably obtained
from revolution counters)
a = area of cake removed by the mud sample tray A = area of screen surface on the filter.
The weight of pol in mud can then be calculated from the cake weight and the pol per cent cake determined on the composited sample. Composite mud samples cannot be effectively held for pol determination for periods much longer than four hours, and analysis of mud samples for pol twice per shift is recommended.
Care of Samplers and Containers
All sugar-mill products are susceptible to rapid deterioration due to bacterial activity; it is therefore imperative t h a t all sample containers be maintained in a thoroughly clean condition and be subjected to frequent sterilization. Sample jars should be washed with hot water after each usage and thoroughly dried. Metal containers (preferably of stainless steel) should be frequently washed and steamed.
Preservation of S a m p l e s
Preservation of certain specific samples has been discussed in this chapter, but details of common preservatives and recommendations for their use will be found in the chapter on laboratory reagents.
C H A P T E R V I I I
LABORATORY R E A G E N T S
This chapter has been re-arranged by listing, wherever possible, the various reagents under each specific analysis. Celite and Triethanolamine, for example, are included under the heading of "Filterability Determination". It is anticipated t h a t this method of presentation will expedite analytical procedure.
P o i s o n s : A good analyst is familiar with the reagents being used and their individual properties. The repeated use of common reagents, however,
C o m m o n Toxic Materials
General Toxicity
Highly toxic. Avoid inhalation of the vapour. Poisonous, combustible, volatile with steam. A narcotic agent with insidious chronic
effects.
Prolonged exposure to low concentrations can result in chronic irritation of the nervous system—an acute narcotic agent in high concentrations.
Highly toxic gas. Not readily detected by the senses at a concentration of one p.p.m. Highly corrosive. Explosive when mixed
with certain organic solvents. Toxic. Included in this table for compara-
tive purposes.
A very poisonous gas. A chemical commonly taken too lightly. Higher concentrations are very dangerous as the sense of smell becomes paralysed.
Cumulative poisons. Refer to the special precautions listed in this chapter. Highly toxic. Can be absorbed via the re-
spiratory tract or by contact with the skin.
Corrosive to all tissues. Permanent damage to the respiratory tract can result from prolonged contact.
Highly corrosive. Severe lung damage can result from inhalation of the vapour. Prolonged exposure to low concentrations
can cause inflammation of nasal and throat tissues.
Narcotic agent. Its toxicity is considered to be associated with the benzene concen- tration present as an impurity. Highly toxic. Do not inhale or allow this
chemical to come in contact Avith the skin. Parts of gas or vapour per million parts of air by volume.
No specific level adopted at this stage by the National Health and Medical Re- search Council of Australia.
84 LABORATORY REAGENTS
c a n t e n d t o a l l o w a " f a m i l i a r i t y b r e e d s c o n t e m p t " a t t i t u d e t o a r i s e . T h e m a j o r i t y of c h e m i c a l s u s e d in s u g a r l a b o r a t o r i e s a r e highly toxic substances, a n d for t h e s a f e t y o f a l l c o n c e r n e d , t h i s p o i n t c a n n o t b e e m p h a s i z e d t o o s t r o n g l y . S o m e g e n e r a l i n f o r m a t i o n o n t h e t o x i c p r o p e r t i e s o f s o m e o f t h e m o r e c o m m o n l y u s e d c h e m i c a l s i n s u g a r l a b o r a t o r i e s i s l i s t e d a b o v e i n t a b u l a r f o r m . T h e m a x i m u m p e r m i s s i b l e l e v e l s i n t h i s t a b l e a r e t h e t h r e s h o l d l i m i t v a l u e s w h i c h h a v e b e e n p r o p o s e d b y t h e A m e r i c a n C o n f e r e n c e o f G o v e r n - m e n t a l I n d u s t r i a l H y g i e n i s t s , a n d w h i c h h a v e a l s o b e e n r e c o m m e n d e d b y t h e N a t i o n a l H e a l t h a n d M e d i c a l R e s e a r c h C o u n c i l o f A u s t r a l i a . H o w e v e r , t h e f a c t t h a t a c h e m i c a l i s n o t l i s t e d i n t h i s t a b l e d o e s n o t n e c e s s a r i l y m e a n t h a t i t i s n o t t o x i c , a n d all l a b o r a t o r y c h e m i c a l s a n d r e a g e n t s s h o u l d b e h a n d l e d a s i f t h e y w e r e p o i s o n o u s . W h e n k n o w n t o x i c o r c o r r o s i v e c h e m i c a l s a r e b e i n g u s e d t h e w e a r i n g o f t h e a p p r o p r i a t e p r o t e c t i v e e q u i p m e n t , s u c h a s g o g g l e s , g l o v e s , a n d r e s p i r a t o r s , i s s t r o n g l y r e c o m m e n d e d . B o i l e r W a t e r A n a l y s i s A l k a l i n i t y
Barium Chloride Solution—Dissolve 10 g of b a r i u m c h l o r i d e B a C l2. 2 H20 i n d i s t i l l e d w a t e r a n d d i l u t e t o 100 m l .
Methyl Orange Indicator—Dissolve 0.10 g of m e t h y l o r a n g e in 100 ml of h o t w a t e r , cool, f i l t e r i f n e c e s s a r y a n d a d j u s t t o v o l u m e .
Phenolphthalein Indicator—Dissolve 1.0 g of p h e n o l p h t h a l e i n in 60 ml o f i n d u s t r i a l m e t h y l a t e d s p i r i t s . W h e n d i s s o l v e d , a d d 4 0 m l o f w a t e r , m i x well, filter i f n e c e s s a r y a n d a d j u s t t o v o l u m e .
Sodium Sulphate Crystals—Reagent g r a d e N a2S 04. 1 0 H2O .
Sulphuric Acid 0 . 0 2 N — D i l u t e 10.0 m l o f 1 . 0 0 N s t a n d a r d s u l p h u r i c a c i d t o 5 0 0 m l w i t h d i s t i l l e d w a t e r . T h e p r e p a r a t i o n o f 1 . 0 0 N s t a n d a r d a c i d i s d e s c r i b e d e l s e w h e r e i n t h i s c h a p t e r .
P h o s p h a t e
Acid Molybdate Solution—Dissolve w i t h o u t h e a t i n g , 8.8 g of a m m o n i u m m o l y b d a t e i n 100 m l o f w a t e r . I n a s e p a r a t e c o n t a i n e r , c a r e f u l l y a d d 3 8 m l o f c o n c e n t r a t e d s u l p h u r i c a c i d t o a p p r o x i m a t e l y 3 0 0 m l o f w a t e r . A l l o w t h e d i l u t e d a c i d t o c o o l t o r o o m t e m p e r a t u r e a n d t h e n t r a n s f e r t h i s s o l u t i o n a n d t h e a m m o n i u m m o l y b d a t e t o a 5 0 0 m l v o l u m e t r i c flask. D i l u t e t o v o l u m e w i t h d i s t i l l e d w a t e r . Hydroquinone—Dissolve 0.5 g of h y d r o q u i n o n e in 50 ml of 0 . 0 2 N s u l - p h u r i c a c i d . S t o r e i n a d a r k o r a m b e r c o l o u r e d b o t t l e . Carbonate—Sulphite Solution—Dissolve 130 g of a n h y d r o u s p o t a s s i u m c a r b o n a t e a n d 2 4 g o f s o d i u m s u l p h i t e ( N a2S 03. 7 H20 ) i n 5 0 0 m l o f w a t e r . H a r d n e s s
Wanklyns Soap Solution—This is u s u a l l y p u r c h a s e d as a p r e p a r e d r e a g e n t f r o m a c h e m i c a l s u p p l i e r .
S o d i u m S u l p h i t e
Potassium Iodate—Iodide Solution—Dissolve 0 . 7 1 3 g of p o t a s s i u m i o d a t e i n 2 0 0 m l o f w a t e r a n d t h e n a d d 7 g o f p o t a s s i u m i o d i d e a n d 0 . 5 g o f s o d i u m b i c a r b o n a t e . W h e n d i s s o l v e d , t r a n s f e r t o a o n e l i t r e v o l u m e t r i c flask a n d d i l u t e t o v o l u m e .
Starch Indicator Solution—Mix 0 . 5 g of s o l u b l e s t a r c h w i t h 5 ml of c o l d w a t e r , a n d t h e n a d d 100 m l o f b o i l i n g w a t e r . H e a t o n a b o i l i n g w a t e r b a t h
LABORATORY REAGENTS 85 for 5 m i n u t e s , c o o l a n d s t o r e i n a r e f r i g e r a t o r . ( A c o m m e r c i a l s o l i d i n d i c a t o r
p r e p a r a t i o n c a n a l s o b e u s e d ) .
Sulphuric Acid, 6.5 per cent v/v.—Carefully a d d 65 ml of c o n c e n t r a t e d s u l p h u r i c a c i d t o a p p r o x i m a t e l y 9 0 0 m l o f d i s t i l l e d w a t e r . C o o l t o r o o m t e m p e r a t u r e a n d d i l u t e t o a v o l u m e o f o n e l i t r e .
S u l p h a t e
Barium Chloride, 0 . 0 4 N — D i s s o l v e 4 . 8 8 6 g of b a r i u m c h l o r i d e ( B a C l2. 2 H20 ) i n d i s t i l l e d w a t e r a n d d i l u t e t o a v o l u m e o f o n e l i t r e .
EDTA—(Diaminoethanetetra—acetic acid, disodium salt), 0 . 0 2 N . — D i s - s o l v e 3.72 g o f E D T A i n d i s t i l l e d w a t e r a n d d i l u t e t o a v o l u m e o f o n e l i t r e .
Hydrochloric Acid, 0 . 5 N approximately—Measure o u t 45 ml of c o n c e n - t r a t e d h y d r o c h l o r i c a c i d ( d 1.18) a n d p o u r i n t o a p p r o x i m a t e l y 5 0 0 m l o f w a t e r . M i x a n d t h e n d i l u t e t o a v o l u m e o f o n e l i t r e .
Solochrome Black Indicator—Weigh o u t 0.5 g of s o l o c h r o m e b l a c k W . D . F . A . a n d d i s s o l v e i n a b o u t 2 m l o f h o t w a t e r . A d d 1 0 g o f s o d i u m c h l o r - i d e , m i x t h o r o u g h l y a n d d r y a t 1 0 5 °C. W h e n d r y , a d d 9 0 g o f s o d i u m c h l o r i d e a n d g r i n d t h o r o u g h l y . T h i s i n d i c a t o r c a n a l s o b e p u r c h a s e d i n t a b l e t f o r m .
Sulphate Buffer Solution—To 5 6 . 5 ml of a m m o n i a (d = 0.880) a d d 4 . 1 2 5 g o f a m m o n i u m c h l o r i d e a n d m a k e u p t o 5 0 0 m l w i t h w a t e r . A d d 3.72 g o f E D T A , m i x a n d t h e n a d d 2 . 0 3 g o f m a g n e s i u m c h l o r i d e ( M g C l2- 6 H20 ) .
B u f f e r S o l u t i o n s
pH 4 . 0 0 Potassium Hydrogen Phthalate Buffer—Dissolve 10.21 g of d r y p o t a s s i u m h y d r o g e n p h t h a l a t e A . R . i n f r e s h l y d i s t i l l e d w a t e r . D i l u t e t o o n e l i t r e . T h e p H o f t h i s s o l u t i o n i s d e f i n e d a s b e i n g 4 . 0 0 a t 1 5 ° C a n d 4 . 0 1 a t 3 0 °C. pH 6.85 Mixed Phosphate Buffer—Dissolve 3.402 g of p o t a s s i u m d i - h y d r o g e n p h o s p h a t e K H2P 04 a n d 4 . 4 5 g o f d i s o d i u m h y d r o g e n p h o s p h a t e N a2H P 04. 2 H20 i n f r e s h l y d i s t i l l e d w a t e r a n d d i l u t e t o o n e l i t r e . T h e p H o f t h i s buffer i s 6.85 a t 2 5 ° C a n d i t h a s a n e g l i g i b l e p H c h a n g e o v e r t h e r a n g e o f o r d i n a r y r o o m t e m p e r a t u r e . pH 9 . 1 8 Borax Buffer—Dissolve 19.071 g of s o d i u m b o r a t e N a2B407. 1 0 H2O i n f r e s h l y d i s t i l l e d w a t e r a n d d i l u t e t o o n e l i t r e . T h e s o l u t i o n h a s a p H of 9.18 a t 2 5 °C a n d 9.07 a t 3 8 °C. C l a r i f i a b i l i t y T e s t Lime-Sucrose Reagent T w o s o l u t i o n s a r e i n i t i a l l y r e q u i r e d : S o l u t i o n A : D i s s o l v e 150 g o f r e f i n e d s u g a r i n a p p r o x i m a t e l y 6 0 m l o f h o t w a t e r . S o l u t i o n B : S l o w l y a d d , w i t h s t i r r i n g , 1 5 g o f A . R . c a l c i u m o x i d e t o 100 m l o f a l m o s t b o i l i n g w a t e r . C a r e f u l l y m i x s o l u t i o n B i n t o s o l u t i o n A . F i l t e r t h e h o t s o l u t i o n t h r o u g h a 6 3 3 A o r s i m i l a r t y p e o f filter p a p e r u n d e r v a c u u m , u s i n g S u p e r c e l f i l t e r a i d . T h e filtered s o l u t i o n m u s t b e s t o r e d i n a r e f r i g e r a t o r , w h e r e i t will k e e p for a p p r o x i m a t e l y t h r e e w e e k s .
F i l t e r a b i l i t y D e t e r m i n a t i o n
Triethanolamine Buffer Solution—Two s o l u t i o n s a r e p r e p a r e d s e p a r a t e l y i n 5 0 p e r c e n t w / w g l y c e r o l s o l u t i o n .
86 LABORATORY REAGENTS
Solution A: Dissolve 15.0 g of A.R. calcium acetate in approximately 300 ml of 50 per cent glycerol solution in a beaker. Mild heating may be used. Solution B: In a second beaker, dissolve 400 g of triethanolamine with approximately 200 ml of 50 per cent glycerol.
N.B.—Triethanolamine can cause severe skin irritation. Avoid direct contact.
Transfer solutions A and B to a one litre volumetric flask and use 50 per cent glycerol to rinse both beakers and to dilute to volume. Mix well and allow to stand overnight.
Add a small quantity of filter aid and filter. Store in a stoppered clear glass bottle.
Celite—This is a standard filter aid No. 505, wrhich has been standardized
by the C.S.R. Company. No other type of filter aid is directly applicable to this test.
Glass Cleaning Solution
Dissolve 80 g of potassium bichromate (K2Cr207) in 300 ml of water in a
litre pyrex beaker and cool to room temperature. Carefully add 460 ml of concentrated sulphuric acid with stirring. The addition of the acid precipitates chromic acid, and the solution will act as an effective cleaning agent while red crystals of this compound are present.
Glass cleaning solution is extremely toxic and highly corrosive. All