Title: Acid preparation of fossils using sulfamic acid, a weak organic acid, and its advantages over acetic and formic acid preparation
1Acid preparation of fossils using sulfamic acid,
a weak organic acid, and its advantages over
acetic and formic acid preparation
- Carlos B. Padilla Mary Luz Parra
- Fundación Colombiana de Geobiología
2Fundacion Colombiana de Geobiologia
3Large Volume of Calcareous Matrix we pursued
less immersions
- Authors of Vertebrate Paleontological Techniques
vol 1 encompass acid preparation with formic and
acetic acids and suggest that discussions with
Daniel Gouget (Institut de Paleontologie du
Museum, Paris) supported their use of formic
acid. - They felt the stronger formic acid was more
stressful to the fossil material but would
require many less immersions than necessary with
acetic acid.
Vertebrate Paleontological Techniques vol.1,
Cambridge University Press, Patrick Leiggi and
Peter May , 1994
4Sulfamic Acid (H2NSO3H)
- Also known as amidosulfonic acid amidosulfuric
acid, sulphamic acid aminosulfonic acid
kyselina aminosulfonova suphamidic acid
sulfamidsäure in German acido sulfamidico in
Spanish acide sulfamidique in French, is a weak
organic acid with marked characteristics that set
it apart from acetic and formic acids - It is a stronger weak acid than both acetic and
formic. - Solid, crystalline powder which dissolves easily
in water. - A powder with melting point of 205C.
- Non hydroscopic.
- Very stable and easy to transport.
- Less toxic
- Good history of use, common in domestic and
industrial cleaning products designed to remove
scale deposits.
5Logarithmic Dissociation Constants (pKa) at 25C
and NFPA Hazard Ratings
NFPA Rating
State fumes pKa health Fire reactivity
Sulfamic Acid solid no 1.18 2 0 0
Formic Acid liquid yes 3.74 3 2 0
Acetic Acid liquid yes 4.76 2 2 2
6Commercial Sulfamic Acid with pH indicator
7The Procedure
- Follows most traditional guidelines.
- Time frames and concentrations varied.
- Initially used all three acids 5 by weight by
volume, eventually reduced to 4 for rapid matrix
removal where significant fossil is not exposed. - Once significant fossil material is exposed, acid
reduced to 2 weight by volume for most work
providing balance between time, number of
immersions and bone integrity.
8Comparative Testing
- Acid bath 100 ml 2 (wbv)
- Sample Matrix size 10 gram fragment
- Cycle time 2hrs.
Sample CBP-17 CBP-4 CBP-21
Formic Acid
Cycles 4 4 7
Start pH 2 2 2
End pH 3 4 2
Residual matrix 0 gms 0 gms 7 gms
Acetic Acid
Cycles 7 6 7
Start pH 2 2 2
End pH 4 3 2
Residual matrix 0 gms 0 gms 7 gms
Sulfamic Acid
Cycles 4 4 7
Start pH 1 1 1
End pH 1 1 1
Residual matrix 0 gms 0 gms 6 gms
9ACID (WASH AND DRY)
Preliminary cleaning
SUFAMIC ACID
PARALOID B-72 in ALCOHOL
Protection with Paraloid B-72
CONTROL (porosity, etc)
NO
OK
Acid Inmersion
SULFAMIC ACID (4-2)
Neutralization
(RUNNING WATER AND DRY )
WASH
Mechanical preparation of soft parts
Ready
More prep. needed
10Pliosaur Specimen FCG-CBP/004
11Chose the segments and tested
12Control of acid activity in fractures
13Repeat same procedure with more segments
12/16/02 Right lateral
01/09/03 Left lateral
01/14/03 Left lateral
01/30/03 Left lateral
14Ventral and Dorsal Views
Sutures and foramina well defined, excess B-72
removed
15Lateral right and left sidesFCG-CBP/004
16Delicate sclerotic rings
17Jan. 1999 Plesiosaur Specimen FCG-CBP/003
18CT Scan as a tool to preview fossil material
while acid cleaning
19Again well defined sutures and foramina
20Ventral view
21Vertebrae also enclosed in calcareous matrix
22Vertebrae ventral and lateral
23Articulated cranium
24Findings
- When all three acids are used for the same period
of time per cycle, formic and sulfamic will
remove the same amount of matrix by weight,
acetic at half the rate. This applies until the
initial pH changes. - Whereas the pH changes with formic and acetic
acids after 2 hrs of work, sulfamic maintains the
original pH up to 12 hrs later allowing for
longer cycles without changing the acid bath.
25Mechanical and Acid vs Acid preparation
- FCG-CBP/3
- Mechanical and Acid preparation
- FCG-CBP/4
- Only acid preparation
- Cycle time 3-5 hrs
- (7) seven cycles with 4 acid.
- (3) three cycles with 2 acid.
- Cycle time 3-5 hrs
- (15) fifteen cycles with 4 acid.
- (6) six cycles with 2 acid.
26Matrix thin sections and residue analysis
Grainstone (Durham 62) Haematite 7 Micro sparite
86
Clay 88 Quartz 5 Opaques 2
FCG-CBP-4
Grainstone (Durham 62) Haematite 8 Micro sparite
87 nummulites
Clay 88 Quartz 2 Opaques 9
FCG-CBP-17
Clay 13 Quartz 4 Opaques 83
Gypsum 47 Haematite 47
FCG-CBP-21
27Conclusions
28Many Thanks to
- Mary Luz Parra, Fundacion Colombiana de
Geobiologia. - Jane Mason, Senior Museum Preparator, University
of California Museum of Paleontology. - Mark Norell, Chairman and Curator Div. of
Paleontology, American Museum of Natural History. - Amy Rachel Davidson, Senior Principal Preparator,
Dept. of Paleontology, American Museum of Natural
History. - Leslie Noè, Curator of Natural Science,
Thinktank, Birmingham Science Museum. - Carlos Jaramillo, Smithsonian Tropical Research
Institute, Panama. - Maria Paramo, Research Professor, Universidad
Nacional de Colombia. - Eugene S. Gaffney, Curator, Dept. of
Paleontology, American Museum of Natural History. - John Maisey, Curator and Axelrod Research Chair,
American Museum of Natural History. - Fernando Etayo, Researcher, INGEOMINAS.
- Diego Pol, M.E.F., Trelew, Patagonia Argentina.
- Marcela Gomez, CASP, University of Cambridge.
- Tatiana Gaona, INGEOMINAS ( Instituto Colombiano
de Geologia y Minas). - Juan de Dios Parra, Fundacion Colombiana de
Geobiologia.