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Updated: May 21, 2025
Cool the filtrate to approximately the standard temperature of the laboratory, and transfer it to a 250 cc. measuring flask, washing out the beaker thoroughly.
The latter cannot exceed 0.01 cc. in accuracy, which corresponds to 0.01 gram. The student should clearly understand that !all other weighings!, except those for calibration, should be made accurately to 0.0001 gram, unless special directions are given to the contrary.
It is desired to dilute a solution of hydrochloric acid to exactly 0.05 N. The following data are given: 44.97 cc. of the hydrochloric acid are equivalent to 43.76 cc. of the NaOH solution. How many cc. of water must be added to 1000 cc. of the aqueous hydrochloric acid? !Answer!: 11 cc.
A steady evolution of gas went on from the 17th to the 18th, 17.4 cc. The liquid, which was turbid on the day after its impregnation, had, in spite of the liberation of gas, again become so transparent that we could read our handwriting through the body of the flask. Notwithstanding this, there was still a very active operation going on in the deposit, but it was confined to that spot.
If it still adheres, a cubic centimeter or so of water may be placed in the cold crucible and cautiously brought to boiling, when the cake will become loosened and may be removed and placed in about 250 cc. of hot, distilled water to dissolve. Clean the crucible completely, rubbing the sides with a rubber-covered stirring-rod, if need be.
In the course of a few days fermentation declared itself: on the 18th it was active; on the 30th it was very active. On June 1st it yielded hourly 35 cc. On the 2nd we began the study of the action of air on the vibrios of this fermentation. We then reversed the flask with the opening under the mercury, and shook it every ten minutes for more than an hour.
!Answers!: 6.67% NaOH; 84.28% Na CO . A sample of sodium carbonate containing sodium hydroxide weighs 1.179 grams. It is titrated with 0.30 N hydrochloric acid, using phenolphthalein in cold solution as an indicator and becomes colorless after the addition of 48.16 cc. Methyl orange is added and 24.08 cc. are needed for complete neutralization. What is the percentage of NaOH and Na CO ?
Acidify the solution with dilute hydrochloric acid, and heat it nearly to boiling. Measure out about 5 cc. in excess of this amount, and pour it into the acid solution. Allow the whole to cool. Decant the clear liquid through a filter, and transfer the precipitate to the filter, using as wash-water a mixture of one volume of concentrated ammonia and three volumes of water.
!Answer!: 1.152 grams. What weight of cream of tartar must have been taken for analysis in order to have obtained 97.60% KHC H O in an analysis involving the following data: NaOH used = 30.06 cc.; H SO solution used = 0.50 cc.; 1 cc. H SO sol. = 0.0255 gram CaCO ; 1 cc. H SO sol. = 1.02 cc. NaOH sol.? !Answer!: 2.846 grams.
Weigh out 25 grams of sodium thiosulphate, dissolve it in water which has been previously boiled and cooled, and dilute to 1000 cc., also with boiled water. They should, therefore, be protected from light and heat. Iodine solutions are not stable for long periods under the best of conditions.
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