We will now proceed to make stock solutions of our different chemicals. First we will make our solution of sulphite soda: We take 1200 grains of the crystals and put them in one of our 16 oz. bottle, adding water to make 15 oz. We will label this on the outside: Stock solution.
Sulphite soda crystals.
One dram equals ten grains.
As there are 1200 grains contained in the 15 oz., which are equal to 120 drams, of course one dram will contain exactly 10 grains. Then we take our carbonate soda crystals, weigh out 1200 grains and put them in a 16 oz. bottle, to which we add water to naake 15 oz. and label this: Stock solution.
Carbonate soda crystals.
One dram equals ten grains.
We do the same with our carbonate potash, making a solution of 1200 grains to 15 oz. water, one dram of which will equal 10 grains. We also do the same with our phosphate soda. It -will be well also to purchase about one dozen common 4 oz. bottles with corks, which will be convenient for holding small quantities of different solutions that will not be nedded in large quantities. In one of the 4 oz. bottles place 20 grains bromide potassium and add water to equal 10 drams and mark this, dram equals one grain. In using bromide of potassium, which is used very largely as a restrainer in development, it is essential that the solution should always be fresh and for that reason only a small quantity should be prepared at a time. The writer makes it a point never to prepare more of the bromide solution than is re quired for use in a few days. It has been found that bromide potassium solution rapidly deteriorates, and if it has been kept sometime it has no effect as a restrainer. With the above stock solutions the amateur will be able to prepare fresh nearly all the ordinary developers, using hydrochinon or pyrogallic acid at a moment's notice, the hydrochinon and pyro being added dry. For example the following is a standard pyro developer greatly used by professional photographers.
No. 1.
Pyrogallic acid, 1 oz.
Sulphite soda cry-stals, 4 oz.; (437i grains to the ounce.) -W-ater to make 32 oz.
No. 2.
Carbonate soda cry-stals, 4 oz.
Water to make 32 oz.
Of this use equal parts Nos. 1 and 2. Now, suppose we require a four ounce developing solution for a 5x8 plate: to make this we should take two ounces each of the above Nos. 1 and 2, and we wish to ascertain exactly how many grains of each of the above chemicals there are in our four ounces of mixed solution. To ascer tain this is very simple. We see that in taking two ounces of No.
1, we take 1-16 of the No. 1, which will contain 1-16 ounce of pyro that equals 27-i grains, 4-16 ounces sulphite soda, that equals 109 grains; and of the No 2, 4-16 ounces carbonate soda, equals 109 grains. Now if the amateur should want to prepare the. above developer, it would not be economical for him to pre pare it as described by the formula. One ounce pyrogallic acid would lose much of its strength long before he had time to use the quantity dissolved . Pyrogallic acid always acts better in the developer when perfectly fresh, and the only way to have it per fectly fresh is to mix it when wanted. Now as we know the quantity of each chemical used in our four ounce solution, we can prepare it perfectly fresh in this way. We need JO9 grains sulphite soda, so we take down our stock solution and pour into our graduate 11 drams, which we know to contain 110 grains, (this is near enough to 109.) We also pour into the same grad uate 11 drams of the carbonate soda crystals solution, giving us 110 grains of that, to which we add water to make the whole up to four ounces. We now carefully weigh out 21 grains of pyro, which, on being poured into the graduate, is instantly dis solved, and the developing solution is ready for use. This formula which we have given above as an illustration, is very strong in pyro, and it would be better for the amateur to weakenit with an equal quantity of water if he wishes to use it for developing plates.
To return once more to our stock solutions. After they have been entirely dissolved they should be filtered. To filter our bottle of sulphite soda we will take another large, clean bottle and place our funnel in it, then take a small wad of fine cotton wool and wet thoroughly under the tap, until it is wet all through, then press this cotton into the bottom of the funnel and slowly pour upon it the contents of our :stock bottle. This should fil ter through slowly, and after it is all filtered, the solution should be returned to the original stock bottle, which has been pre viously thoroughly cleaned. In the same way the other solutions should be filtered. Of course the same cotton must not be used for filtering any other substance, and the funn.el should be very clean before being used on any other chemical. One caution must be observed throughout: the hyposulphite soda _must be kept apart from all other chemicals, and no bottle that has con tained any hypo. should ever be used for any other purpose.