EQUIPMENT REQUIRED LIST BELOW:
1. THREE PLASTIC TUB (POLYTHRLENE OR PVC ) OF THE SIZE OF FILMS.
2. ONE PLASTIC DRUMS 60 TO 90 LITERS CAPACITY.
3. ONE PLASTIC BUCKET ABOUT 20 LITERS CAPACITY.
4. ONE PLASTIC MUG/BOWL.
5. ONE PAIR HAND GLOVES PVC OR RUBBER.(ACID AND ALKALI PROOF).
6. FIFTY CLIPS TO HOLD THE FILMS AND HANG.
7. TWO PERFORATED PLASTIC BOWLS.
8. ONE IRON SPATULA (KHONCHA).(FOR STIRRING WHILE DRYING).
9. ONE STAINLESS STEEL SPOON.
10. ONE IRON KADAI (FRYING PAN) (FOR DRYING).
11. ONE SIGRI OR STOVE (FURNACES).
12. WOODEN STICK.
13. CAUSTIC SODA CRYSTALS.
14. SODIUM NITRATE POWDER.
15. BOREX POWDER.
16. SODIUM CARBONATE(SODA ASH) POWDER.
17. ALUM.
THEORY:-
In black & while exposed films and papers , there are two types of portions visible one is black opaque and other is transparent . The black portion is the deposit of silver and we have to remove this from the plastic film to recover silver . Greater black area will have greater percentage of silver. If white transparent is more, then the silver content will be less. Though the exact percentage of silver present can not be given , yet normally the following data can be considered for estimated:-
1. X-RAY clinic films used and in mixed sizes :- 8 to 20 gms / Kg.
2. cine films (black and white) :- 4 to 6 gms / Kg.
3. photographic films (black and white) :- 4 to 6 gms /Kg.
4. bromide papers :- 2.5 to5 gms /kg.
RECOVERY OF BLACK DEPOSITS FROM FILMS
Put on the pvc hand gloves and perform the following process:-
1. Take a plastic tub (call it A) and fill it with about 10liters og hot water and dissolve about 500gms of caustic soda crystals in it. stir the liquid by means of wooden stick.
2. Take about 5Kg of X-RAY films and dip the film one by one in the caustic soda solution one above other such that coated side (rough side) of the films are up side.
If its cine film then dip the whole roll in the caustic soda solution duly spreading the coil such that the solutiob reaches every place.
Note:-
Concentration of caustic soda can be increased if fast results are required.more the concentration more speedy will be the work . Keep the tub A with films for about 4 to 12 hours for completion of the chemicals reaction to loosen the black deposits on the plastic films.
3. Take 2nd plastic tub and fill it with about 20 liters or more water and call it tub B.similarly,take 3rd plastic tub and fill it with water and call it tub C.in both tub , use ordinary cold water.
4. X-RAY FILMS :- After about 12 hours (there is no harm if it remains for longer time) put on the hand gloves. rub the coated side of one of the film of tub a with hand to remove loodened black deposits. Remove all the deposits material by repated rubbing and let the material go in the solution. Rinse the films in the solution so it becomes completely transparent.Now rinse the film in tub b so that the remaining material will go in this water and the plastic films will be clearer . Finally rinse the film in the tub c so that if any material remains finally goes in the water.
CINE FILM ROLL:- Wash it lengthwise from one end to last end in tub a , b and then in c.
5. Hold the X-RAY films by clip (clips used for hanging cloths can be used) and hang it on a string such that one corner of the film is perpendicular to the land to allow the water to drip off and dry and dry the film. it will take nearly 1 to 3 hours to dry. Oven can also be used for fast drying . Sililarly cine films rolls may be hanged suitably to dry.
6. Collect the dried films and repeat the process 1 to 5 with remaining all the films in tub a. while washing every care should be taken that the films is perfectly clear and there are no scratches on it. This can be sold in the market and used in the manufacture of greeting card, purse, office files, screen printing, electric table lamps and shades, packing of readymade garments etc. Cone films rolls are used in the manufacture of bangles, photographic films are in small sizes and hence don't have any market. These washed films are having films are having a good in market in mumbai, delhi, calcutta and madras etc.
Note: During this process few of the washed films may be deshaped and wasted and are of no use. Consider this wastage to be of about 10% maximun.
7. Collection of material by sedimentation:
Now transfer all the liquids of tub A,B,and C in a plastic drum of capacity of about 60 to 90 liters. Add 75 gms to 100 gms approx. alum and stir it.Leave the drum undisturbed for about 2 to 3 days till all the suspended black particles settles down in the bottom and transparent clear or coloures liquid remains on the top.
8. After 2 to 3 days when all the suspended particles have settled down in the bottom , then gently take out the liquid from the top without disturbing the settled material by means of plastic mug/bowl and throw it away. This may also be removed by siphon by plastic pipe , if desired,precaution should be taken that the settled undissolved material should not be thrown away beacause this will turn to silver . When this is done there remains sludge (black mud like material) in the bottom.
9.FILTRATION: The filtration can be done by two ways:
a) Take a unbleached long cloth bag and hang it on a rod. Now, gently pour the sludge collected from bottom by sedimentation. First for about 2 minutes some precipitates of silver will also come out from bag along with liquid.so collect this liquid and put it back in the back in the bag. Afterward only clear waste liquid will pass through the bag, while silver compound will remain in the bag as residue. This will take 6 to 12 hour for filtration but if it is kept for more time then it will be more and more filtered and dried, and is better.
b) take a hemispherical shape plastic perforated bowl and spread two fold news paper (preferably yellow type) and gently pour the sludge collected from bottom by sedimentation. Waste clear liquid will pass through the news paper while silver compound will remain in the paper as residue. This will take 6 to 12 hours for filtration but if it is kept for more time then it will be more filtered and dried, and it better. check the filtrate liquid and see that if there is any black powder or particles in the liquid.if particles are there,then again di the sedimentation to collect the particles which are of silver. if there is no paricles then throw away the solution. Heat the silver compound in an iron kadai (frying pan/vessel) and stir it with the help of spatula till silver compound is dried and all the glass have been removed. stove, sigri or furnace may be used for heating. There is no harm if it is highly heated to red hot temperature. Let the material cool and then collect it. If any material sticks to kadai/vessel, then remove it by hammering. When bag get spoiled burn the bag and mix its ash with dried compound. Similarly paper can be burned and mix its ash with dried compound.
Melting
10. Prepare a proportionable mixture of the following chemicals:
a) Dried black powder of process No 10............1Kg
b) sodium nitrate powder ....................................1Kg
c) Borex powder..................................................500 gms
d) Soda ash (sodium carbonate)............................250 gms
Purchase commercial pure material from reliable chemical dealers, otherwise there is the possibillities of unsatisfactory results. Mix them by hand. Get it melted by silver melter or goldsmith before your eyes and give him the following hints:- Take the material in a new graphite or silicon crucible. Take another used crucible of the same size and remove its bottom. Put this crucible inverted i.e. upside down on the crucible which contains the mixture to prevent overflow of the material when it boils. Heat it. The material will first get melted and then boil. Now stop the blower of the furnace and let it heat for some time till the boiling stops and the whole material sets at the bottom in the from of liquid.stir it by means of long iron rod and see that the whole material is throughly mixed and melted. Now again start the blower to supply high temperature. Over heating will not harm but under heating will not reduce the silver completely. Heat the material till the volume of the mass reduces to nearly 1/4 and see that there is no further reduction in volume. Now heating is completed. This process will take approx. 30 to 60 min.
CASTING:-
Take a rectangular cast iron mould, slightly warm it on the furnace and oil it and then keep it in a standing position so that the silver being heavy and hence will form one block of silver. Pour the red hot material into the mould from the side of the lower level. Pour the material gently with a particular normal speed and do not invert the crucible immediately. Wait till it leaves off its redness. Then drop it on the earth and apply few strokes of hammer and block of silver will seperate out. Reset of the material is to be checked and thrown out.
IF BLOCK OF SILVER DOES NOT COME UP:-
Either it is under heated or chemicals mixed are not pure or the black sludge was not dried properly i.e. The gases were not removed in heating was stopped before all gases were removed, in all sich cases, crush the material to sand like powder and mix about 50% of the pure chemicals and again repeat the process in the furnace and sufficient temperature should be given. You must get the block of silver. Further if the block of silver you obtain is blackish in colour then again melt the block in another crucible without any chemicals and you will get brilliant white silver block.
