“se 
J. M, Ordway on Nitrates of Iron. 
Such acid of sp. gr. 1°34, at 65° C., rendered the steel passive; with 
€ initial temperature 65°6° it continu o act, 
the initial temp 65°6° it ed to act 
cid of sp. gr. 1:335, at 58°3° C., soon ceased to act; with such acid 
of sp. gr. 1°33, at 49° 4° a the action was momentary ; 
with this ‘acid first heated to 50° there stoppage. 
id acid of sp. gr. 1°327 the limit of passivity lay between 47°2° and 
AG. 
Acid of sp. gr. 1-32 at 32-2° induced passivity; with the same acid at 
32°8° the action continued. 
With cast iron the limit of passivity cannot be so precisely 
defined. Acid of moderate strength often continues to dissolve 
the iron y ery slowly me tate after the first momentary, vio- 
| lent pre is over. fe ving been found by many trials that 
may occur i ape iron even with acid of as low sp. gr. 
aw 20, the ollowinis “definite experiments were made: 
—Took in each case a tared lump of iron weighing between 2-8 
aa 3: 3 grams, and some acid at 25°5° C. At the end of aces hours the bits 
of iron were cleaved of the loosened carbon, washed, tay and weighed. 
ith acid of sp. gr. 1 sir the i iron had lost 0218 g. 
“ 19 0 290 
&s 6 : ‘18 é “ 0:386 
“ “ 117 “ “ 1497 © 
“ & 1:16 * KA 1529 
“ “ 115 “ad « 1512 
114 4 
With the ies ria the apparent pa ae but five minutes, and in 
the next two cases we evolution 0 Eats anes or what longer. In 
Ms were tried, each with 20 ¢ 
gta 
hours the product s were elaine basic pernitrates, turbid fookias but 
qu 
te soluble in water. 
With acid of sp. gr. : 18 thei iron had lost “ . te. 
175 
“ “6 - ~ a ~ 
“ “ © 2°246 
“ 15 “ “ts a 
1 
at -—Another ee of cast nen ie in pieces weighing between 2°7 and 
n each instance 20 c¢.c. of acid at 23°C. At 
end of nine sae the iron in acid a of sp. gr. ee had. lost 0 = g 
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