On Citric Acid. 105 



specific gravity of 1*0312 (16 ounces 8 drachms) to that of 

 1*0G2^', oi 17 ounces avoirtlupois the v/ine puit. 



Should the parcel appear good by the hydrometer, take then, 

 for the next experiment, a wine glass oF the juice, dilute it plen- 

 tifully with pure water, and add to it a tew drops of a solution 

 of acetate of lead, as directed at page 51 : this will produce an 

 immediate precipitate, chiefly of citrate of lead, which should 

 then be treated with a little pure nitrous acid, and the effect 

 carefully observed; for, if the nitrous acid dissolve the whole of 

 the precipitate, it will prove that the juice under examination 

 contains no sulphuric acid. By proceeding in the same way 

 with an acidulous solution of nitrate of silver *, instead of acetate 

 of lead, it will be seen whether the juice contains any muriatic 

 acid ; this and the sulphuric being the only two acids, except the 

 acetic, that are ever likely to be employed in the adulteration of 

 lemon-juice. 



There were indeed instances, when lomon-juice was scarce in 

 the market, of its being adulterated with vinegar ; and should 

 this occur again, it maybe readily detected by saturating a sam- 

 ple of the juice with carbonate of lime (whiting or pure chalk), 

 and when the calcareous citrate precipitates, taking the specific 

 gravity of the supernatant liquor. For, as lime is entirely solu- 

 ble in acetic acid, part of the whiting employed will be held in 

 solution by the vinegar, and occasion the supernatant liquor to 

 be specifically heavier than it would have been had the sophisti- 

 cation not been practised. 



To render tliis fact more certain, I made the following experi- 

 ment. Having purchased a few good lemons, and pressed out 

 the juice, 1 found its spec, gravity to be 1'03S4. This was put 

 into a capacious phial bottle, and when loosely corked was placed 

 in a secure place in my common sitting-room, the temperature 

 of which was usually at about 60 degrees. When it was ex- 

 ^ amined at the end of sixteen days, the mucilage had in a great 

 measure deposited, and the specific gravity of the juice was found 

 reduced to that of 1-0352. 



The weight of the juice under experiment, and after it had 

 passed the filter, was 2400 grains, and the deposited mucilage 

 weighed 133 grains, or one nineteenth of the whole. 



The clear juice being divided into two equal portions, to one 

 of them a fourth of its weight of common vinegar was added. 

 Finding that the unadulterated portion amounted to 1200gVains, 



• To prepare the nitrate of silver, dissolve a drachm of lunar caustic, v/hicli 

 may be procured from any respectable apothecary, in one ounce of 30ft water, 

 and to this add half an ounce of stro.'g nitrovis acit!, previously diiutcid with nn 

 equal portion of water. AVJicn the impurities h:ivo precipitated, pi^)ur ofl' tl-.c 

 clear supernatant lii^uor, and preserve it iu a slopped phial I'or u^c. 



an 



