MEAT AND MEAT PRODUCTS. 



15 



volume of nitric oxid with that evolved by a definite volume (f> to Id cc) of normal 

 sodium nitrate solution. 



(b) PHENOL-8ULPHONIC ACID METHOD.* 



Weigh 1 gram of the sample into a 100-cc flask, add from 20 to 30 cc of water, and 

 heat on the water bath for fifteen or twenty minutes, shaking occasionally. Add 3 cc 

 of a saturated solution of silver sulphate for each per cent of sodium chlorid present, 

 then add 10 cc of lead subacetate and 5 cc of alumina cream, shaking after each 

 addition. Make up to mark with water, and filter through a fluted filter, returning 

 the filtrate to the filter until it runs clear. Evaporate to dryness 25 cc of the filtrate, 

 add 1 cc of phenol-sulphonic acid," mix thoroughly with a glass rod, add 1 cc of 

 water and 3 or 4 drops of concentrated sulphuric acid and heat on a steam bath for 

 two or three minutes, being careful not to raise the temperature sufficiently to char 

 the material. Now add about 25 cc of water and an excess of ammonium hydroxid. 

 Transfer to a 100-cc flask, add 1 or 2 cc alumina cream if not perfectly clear, dilute to 

 mark with water, and filter if necessary. 



Prepare a number of 50-cc Nessler tubes, preferably the long, narrow tubes, placing 

 in the first 1 cc of the standard nitrate solution, in the second 2 cc, and so on to 10 cc, 

 then 12 cc, 15cc, 18cc,and20 cc. The comparison of the solution under examination 

 with these tubes will show directly if it comes within this range, in which case it can 

 be read by direct comparison with the various tubes till the one of the exact shade is 

 found. If the color of tj^e solution be darker than any of the tubes prepared as above, 

 it is preferable to dilute as many times as may be necessary to bring the color within 

 this range by transferring 25 cc of the solution to another tube with a pipette and 

 filling up to the mark with distilled water. In this case the reading of the diluted 

 solution in cubic centimeters of standard solution should be multiplied by the num- 

 ber of times the solutii >n under comparison has been diluted. More exact comparisons 

 can be made looking sidewise through the tubes toward a window covered with white 

 paper and shaded from direct sunlight. 



The following table prepared by Mr. Given enables one to determine at a glance 

 the percentage of potassium nitrate in a given sample from the number of cubic 

 centimeters of standard solution employed, if the above directions are followed in 

 detail : 



Per cent potassium nitrate. 



Thismethod is a modification of the one ordinarily employed for determining potassium nitrate 

 in water. It was a<Iapu-d to tlu> examination of meat by Mr. Arthur Given. 



' Prepared l.y mixing together 37 re of romvnt rated sulphuric acid, 3 cc of distilled water, and <> 

 Kramsof phenol. 



