jiBhn «f i^itre upon Platina and Silver. 31 



fefaving found that nitrei would diflblvc gold, I tried whether it would produce any effeft 

 upon platina. 



It has been forpierly obferved, that the grains of platina, in the impure ftate in which it 

 is originally found, might, by being long heated in a crucible with nitre, be reduced to pow- 

 der. Lewis, from his own experiments and thofe of MargrafF, thought that the iron only 

 which is contained in the grains of platina was corroded by the nitre. But by heating 

 nitre with fome thin pieces of pure platina in a-cup of the. fame metal, I found that the 

 platina was eafily diffolved, the cup being much corroded, and the thin pieces entirely de- 

 ftroyed. By diflblving the faline matter in water, the greater part of the platina was pre- 

 cipitated in the form of a brown powder. This powder, which was entirely foluble in 

 marine acid, confided of the calx of platina, combined with a portion of alkali, which 

 could not be feparated'by being boiled in water. The platina which was retained by the 

 alkaline folution communicated to it a brown yellow colour. By adding an acid to it a 

 precipitate was formed, which confided of the calx of platina, of alkali, and of the acid 

 which was employed. 



Silver I found to be a little corroded by nitre : but, as its action upon that metal was 

 very inconfiderable, it did not appear to be deferving of a more particular examination. 



IX. 



An Account of certain Gaufes of Alteration injurious to the ^lality of Corn, and the Means of pre- 

 venting this Change *. By B. G. Sage, of the ci-devant Academy of Sciences, Profejfor of 

 Chemijiry and Mineralogy in the School des Mines de la Monnoie. 



I 



N the Analyfis of Corn,, which I publiflied in 1776, I have diewn that when the corn no 

 longer contains glutinous f or ve^eto-animal matter, it affords flour not adapted to produce 

 a good panary fermentation ; that the bread is not white, and has a difagreeable fade and 

 fmell j that it produces an opprefEon at the domach, putrid diforders, and the dry gangrene, 

 like fmutted ryCi I did not at that time know the caufe of this alteration of corn ; but 

 difcovered it lad year, by attending to the farming operations in the corn country of 

 Beauce, where I have obferved that the method of houfing or dacking the corn Was more 

 fuited to dedroy than to preferve it. 



In fa£l, the fickle has fcarcely cut the corn before it is colle£led in fheaves to form fhocks,. 

 or larger parcels, which are immediately conveyed into the barns, where they are packed 



does not contain its full, proportion of oxygen, occafions the fame precipitation, unlefs it is very ftrong; and if a 

 mixture of fuch ftrong nitrous acid, and of a folution of gold in nitrous acid, is dropped into water, the gold is 

 deprived of itS|Oxygen, and is precipitated of a blue colour. Two caufes contribute to produce this elfeft upon 

 the addition of water. The adhefion of the calx of gold to nitrous acid is by that means weakened, and the 

 oxygen is attrafted more ftrongly to the imperfeft nitrous acid in confequence of their attraftion for water when 

 they are united. 



* Journal de Phyf. Sep. for 1794. 



t Wheat is compofed of the cortical part called bran, ftarch, faccharine matter, and the glutinous fubftancc. 

 The fl<ur obtained at the mills near Paris is compofed of i-i6th part of faccharine and extraftive matter, 

 j.jds ,: white fecula called ftarch, and i-4th part of elaftic glutinous matter. The corn of tbefouthern coun- 

 tries contain more. S. ^ 



5 a8> 



