1258:
276:, while its symbol ("Torr") is always written with an uppercase initial; including in combinations with prefixes and other unit symbols, as in "mTorr" (millitorr) or "Torr⋅L/s" (torr-litres per second). The symbol (uppercase) should be used with prefix symbols (thus, mTorr and millitorr are correct, but mtorr and milliTorr are not).
295:
to the general public. He is credited with giving the first modern explanation of atmospheric pressure. Scientists at the time were familiar with small fluctuations in height that occurred in barometers. When these fluctuations were explained as a manifestation of changes in atmospheric pressure, the
303:
Over time, 760 millimeters of mercury at 0 °C came to be regarded as the standard atmospheric pressure. In honour of
Torricelli, the torr was defined as a unit of pressure equal to one millimeter of mercury at 0 °C. However, since the acceleration due to gravity – and thus the weight of a
364:
that depend on an assumed density of a fluid and an assumed acceleration due to gravity. The use of these units is discouraged. Nevertheless, manometric units are routinely used in medicine and physiology, and they continue to be used in areas as diverse as weather reporting and scuba diving.
506:
The difference between one millimeter of mercury and one torr, as well as between one atmosphere (101.325 kPa) and 760 mmHg (101.3250144354 kPa), is less than one part in seven million (or less than 0.000015%). This small difference is negligible for all practical purposes.
576:
These four pressure units are used in different settings. For example, the bar is used in meteorology to report atmospheric pressures. The torr is used in high-vacuum physics and engineering.
339:
of one atmosphere. This yields a precise definition that is unambiguous and independent of measurements of the density of mercury or the acceleration due to gravity on Earth.
373:
The millimeter of mercury by definition is 133.322387415 Pa (13.5951 g/cm × 9.80665 m/s × 1 mm), which is approximated with known accuracies of density of mercury and
316:
1095:
Devices similar to the modern barometer, using water instead of mercury, were studied by a number of scientists in the early 1640s (see
283:, the unit measuring the strength of a magnetic field. Although frequently encountered, the alternative spelling "Tor" is incorrect.
602:
1099:). Torricelli's explanation of the principle of the barometer appears in a letter to Michelangelo Ricci dated 11 June 1644.
1226:
1205:
348:
1257:
396:
of one standard atmosphere, while the atmosphere is defined as 101325 pascals. Therefore, 1 Torr is equal to
1159:
235:
1278:
1172:
1062:
595:
144:
17:
1288:
1283:
1248:
1184:
Note that a pressure of 1 bar (100000 Pa) is slightly less than a pressure of 1 atmosphere (101325 Pa).
627:
1209:
588:
637:
253:
68:
227:
162:
31:
279:
The torr is sometimes incorrectly denoted by the symbol "T", which is the SI symbol for the
622:
231:
8:
1052:
1047:
304:
column of mercury – is a function of elevation and latitude (due to the rotation and non-
292:
1222:
1201:
1142:
1042:
199:
93:
234:
made them slightly different (by less than 0.000015%). The torr is not part of the
374:
1197:
1096:
1057:
125:
1262:
1109:
179:
1272:
1072:
1067:
612:
320:
256:, an Italian physicist and mathematician who discovered the principle of the
239:
219:
134:
1241:
291:
Torricelli attracted considerable attention when he demonstrated the first
280:
297:
273:
175:
319:
to the currently accepted definition: one atmosphere is equal to 101325
1130:
617:
305:
257:
445:
The relationship between the torr and the millimeter of mercury is:
308:
of the Earth), this definition is imprecise and varies by location.
1077:
439:
50:
1221:
DeVoe H. Thermodynamics and
Chemistry. Prentice-Hall, Inc., 2001,
510:
In the
European Union, the millimeter of mercury is defined as
572:
The atmosphere (symbol: atm), defined as 101.325 kPa exactly.
242:
226:
Historically, one torr was intended to be the same as one "
438:) is an infinitely long, periodically repeating decimal (
1246:
349:
Pressure measurement § Liquid column (manometer)
1156:
BS 350: Part 1: 1974 – Conversion factors and tables
1198:
Quantities, Units and
Symbols in Physical Chemistry
569:The bar (symbol: bar), defined as 100 kPa exactly.
263:
1270:
342:
317:10th General Conference on Weights and Measures
596:
412: Pa. The decimal form of this fraction (
238:(SI). Even so, it is often combined with the
1200:, 3rd ed. Royal Society of Chemistry, 2007
1143:National Physical Laboratory: Pressure units
230:", but subsequent redefinitions of the two
603:
589:
202:(101325 Pa). Thus one torr is exactly
14:
1271:
145:British Gravitational System
368:
1131:BIPM – Resolution 4 of the 10th CGPM
24:
25:
1300:
1235:
565:Other units of pressure include:
323:. The torr was then redefined as
1256:
1029:
951:
866:
799:
738:
666:
311:In 1954, the definition of the
1215:
1187:
1178:
1166:
1148:
1136:
1124:
1102:
1089:
264:Nomenclature and common errors
13:
1:
1160:British Standards Institution
1110:"Rules and style conventions"
1083:
236:International System of Units
1173:Council directive 80/181/EEC
1063:Outline of the metric system
343:Manometric units of pressure
249:(mTorr) or 0.001 Torr.
27:Traditional unit of pressure
7:
1036:
10:
1305:
346:
286:
29:
584:
252:The unit was named after
140:
121:
117:
99:
74:
64:
56:
46:
41:
1097:History of the Barometer
380:The torr is defined as
358:millimeters of mercury
254:Evangelista Torricelli
69:Evangelista Torricelli
638:Pound per square inch
228:millimeter of mercury
182:, defined as exactly
32:Torr (disambiguation)
1242:NPL – pressure units
623:Technical atmosphere
362:centimeters of water
223:(≈ 133.32 Pa).
174:(symbol: Torr) is a
30:For other uses, see
1279:Non-SI metric units
1162:. 1974. p. 49.
1053:Conversion of units
1048:Centimetre of water
628:Standard atmosphere
581:
514:1 mmHg = 133.322 Pa
315:was revised by the
112:... is equal to ...
1175:(20 December 1979)
579:
369:Conversion factors
356:are units such as
150:
142:
131:
123:
1289:Mercury (element)
1284:Units of pressure
1193:Cohen E. R.
1043:Atmosphere (unit)
1034:
1033:
293:mercury barometer
168:
167:
100:Conversions
16:(Redirected from
1296:
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1134:
1128:
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1121:
1119:
1117:
1106:
1100:
1093:
1027:
1026:
1023:
1016:
1015:
1012:
1005:
1004:
1001:
994:
993:
990:
983:
982:
979:
975:
963:
962:
959:
949:
948:
945:
939:
937:
936:
933:
930:
922:
921:
918:
911:
910:
907:
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899:
896:
884:
883:
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859:
858:
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849:
836:
835:
832:
829:
822:
821:
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813:
810:
807:
797:
796:
789:
787:
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771:
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736:
725:
724:
721:
718:
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706:
704:
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693:
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673:
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591:
582:
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375:standard gravity
354:Manometric units
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332:
329:
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197:
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194:
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176:unit of pressure
160:
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132:
126:SI derived units
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92:
90:
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83:
39:
38:
21:
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1137:
1129:
1125:
1115:
1113:
1108:
1107:
1103:
1094:
1090:
1086:
1058:Inch of mercury
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1024:
1021:
1019:
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1010:
1008:
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997:
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988:
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977:
973:
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713:
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700:
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671:
609:
580:Pressure units
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157:
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130:
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87:
84:
81:
80:
78:
35:
28:
23:
22:
15:
12:
11:
5:
1302:
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1265:
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1244:
1237:
1236:External links
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1231:
1214:
1210:IUPAC pdf copy
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1177:
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1070:
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1055:
1050:
1045:
1038:
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1032:
1031:
1028:
1017:
1006:
995:
984:
969:
968:1 lbf/in
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964:
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950:
923:
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871:
868:
865:
860:
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837:
823:
815:
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781:
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370:
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272:is written in
268:The unit name
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198:of a standard
180:absolute scale
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133:133.3224
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1227:0-02-328741-1
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1206:0-85404-433-7
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1073:Pressure head
1071:
1069:
1068:Pascal (unit)
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442:length: 18).
441:
378:
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284:
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255:
250:
248:
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241:
240:metric prefix
237:
233:
229:
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181:
177:
173:
164:
148:
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139:
136:
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33:
19:
1217:
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1189:
1180:
1168:
1155:
1150:
1138:
1126:
1116:29 September
1114:. Retrieved
1104:
1091:
889:1 Torr
632:
575:
564:
553:
548:
532:
527:
517:
509:
505:
494:
489:
484:
466:
461:
456:
444:
379:
372:
361:
357:
353:
352:
312:
310:
302:
290:
278:
269:
267:
251:
246:
245:to name one
225:
178:based on an
171:
169:
111:
106:
105:1 Torr
47:Unit of
36:
841:1 atm
731:1 bar
298:meteorology
296:science of
65:Named after
18:Torr (unit)
1273:Categories
1084:References
780:1 at
664:1 Pa
347:See also:
313:atmosphere
306:sphericity
300:was born.
274:lower case
200:atmosphere
75:Definition
659:(lbf/in)
543:1 mmHg =
522:1 Torr =
477:1 mmHg =
449:1 Torr =
260:in 1644.
258:barometer
247:millitorr
1078:Pressure
1037:See also
440:repetend
51:pressure
1263:Physics
938:
926:
893:133.322
818:735.559
726:lbf/in
710:1 Pa =
699:1 Pa =
688:1 Pa =
677:1 Pa =
670:1 Pa =
656:(Torr)
414:133.322
410:
398:
394:
382:
337:
325:
321:pascals
287:History
220:pascals
217:
205:
196:
184:
91:
79:
1249:Portal
1225:
1204:
1195:et al.
1112:. NIST
1020:51.714
874:14.695
863:1.0332
826:14.223
765:14.503
759:750.06
744:1.0197
701:7.5006
690:9.8692
679:1.0197
653:(atm)
647:(bar)
613:Pascal
518:hence
401:101325
208:101325
161:
107:in ...
57:Symbol
1009:0.068
998:0.070
987:0.068
956:0.019
942:0.001
915:0.001
904:0.001
855:1.013
804:0.967
793:0.980
750:0.986
712:0.000
707:Torr
650:(at)
644:(Pa)
545:0.999
524:1.000
479:1.000
451:0.999
281:tesla
243:milli
232:units
153:0.019
1223:ISBN
1202:ISBN
1118:2012
976:.757
882:5142
870:760
834:1203
820:2401
812:3541
696:atm
674:bar
633:Torr
561:Torr
540:mmHg
502:Torr
474:mmHg
270:torr
172:torr
170:The
60:Torr
42:torr
1025:572
1022:932
1014:964
1011:045
1003:958
1000:306
992:573
989:947
981:168
978:293
974:894
961:775
958:336
947:789
944:315
935:760
917:359
909:224
906:333
898:421
895:368
879:775
876:948
848:325
846:101
831:307
828:343
809:105
806:841
795:665
786:066
773:022
770:773
767:773
723:730
720:737
717:037
714:145
685:at
618:Bar
558:...
554:236
537:...
533:763
499:...
495:321
490:466
485:142
481:000
471:...
467:699
462:533
457:857
453:999
432:947
429:578
426:631
423:052
420:421
418:368
407:760
391:760
360:or
334:760
214:760
193:760
163:psi
155:336
94:atm
88:760
1275::
1212:).
1158:.
1030:—
952:—
940:≈
920:51
867:—
857:25
853:≡
844:≡
800:—
788:.5
784:98
763:=
757:=
752:92
748:=
742:=
739:—
735:10
705:10
694:10
683:10
672:10
667:—
547:99
526:00
377:.
158:77
135:Pa
1251::
1229:.
1208:(
1145:.
1133:.
1120:.
972:6
932:/
929:1
703:×
692:×
681:×
604:e
597:t
590:v
549:7
528:2
404:/
388:/
385:1
331:/
328:1
211:/
190:/
187:1
85:/
82:1
34:.
20:)
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